1570 lines
56 KiB
Plaintext
1570 lines
56 KiB
Plaintext
@node Error Reporting, Memory, Introduction, Top
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@chapter Error Reporting
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@c %MENU% How library functions report errors
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@cindex error reporting
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@cindex reporting errors
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@cindex error codes
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@cindex status codes
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Many functions in @theglibc{} detect and report error conditions,
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and sometimes your programs need to check for these error conditions.
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For example, when you open an input file, you should verify that the
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file was actually opened correctly, and print an error message or take
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other appropriate action if the call to the library function failed.
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This chapter describes how the error reporting facility works. Your
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program should include the header file @file{errno.h} to use this
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facility.
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@pindex errno.h
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@menu
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* Checking for Errors:: How errors are reported by library functions.
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* Error Codes:: Error code macros; all of these expand
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into integer constant values.
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* Error Messages:: Mapping error codes onto error messages.
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@end menu
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@node Checking for Errors, Error Codes, , Error Reporting
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@section Checking for Errors
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Most library functions return a special value to indicate that they have
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failed. The special value is typically @code{-1}, a null pointer, or a
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constant such as @code{EOF} that is defined for that purpose. But this
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return value tells you only that an error has occurred. To find out
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what kind of error it was, you need to look at the error code stored in the
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variable @code{errno}. This variable is declared in the header file
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@file{errno.h}.
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@pindex errno.h
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@deftypevr {Variable} {volatile int} errno
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@standards{ISO, errno.h}
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The variable @code{errno} contains the system error number. You can
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change the value of @code{errno}.
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Since @code{errno} is declared @code{volatile}, it might be changed
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asynchronously by a signal handler; see @ref{Defining Handlers}.
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However, a properly written signal handler saves and restores the value
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of @code{errno}, so you generally do not need to worry about this
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possibility except when writing signal handlers.
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The initial value of @code{errno} at program startup is zero. In many
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cases, when a library function encounters an error, it will set
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@code{errno} to a non-zero value to indicate what specific error
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condition occurred. The documentation for each function lists the
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error conditions that are possible for that function. Not all library
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functions use this mechanism; some return an error code directly,
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instead.
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@strong{Warning:} Many library functions may set @code{errno} to some
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meaningless non-zero value even if they did not encounter any errors,
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and even if they return error codes directly. Therefore, it is
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usually incorrect to check @emph{whether} an error occurred by
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inspecting the value of @code{errno}. The proper way to check for
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error is documented for each function.
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@strong{Portability Note:} @w{ISO C} specifies @code{errno} as a
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``modifiable lvalue'' rather than as a variable, permitting it to be
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implemented as a macro. For example, its expansion might involve a
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function call, like @w{@code{*__errno_location ()}}. In fact, that is
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what it is
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on @gnulinuxhurdsystems{}. @Theglibc{}, on each system, does
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whatever is right for the particular system.
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There are a few library functions, like @code{sqrt} and @code{atan},
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that return a perfectly legitimate value in case of an error, but also
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set @code{errno}. For these functions, if you want to check to see
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whether an error occurred, the recommended method is to set @code{errno}
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to zero before calling the function, and then check its value afterward.
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@end deftypevr
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@pindex errno.h
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All the error codes have symbolic names; they are macros defined in
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@file{errno.h}. The names start with @samp{E} and an upper-case
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letter or digit; you should consider names of this form to be
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reserved names. @xref{Reserved Names}.
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The error code values are all positive integers and are all distinct,
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with one exception: @code{EWOULDBLOCK} and @code{EAGAIN} are the same.
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Since the values are distinct, you can use them as labels in a
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@code{switch} statement; just don't use both @code{EWOULDBLOCK} and
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@code{EAGAIN}. Your program should not make any other assumptions about
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the specific values of these symbolic constants.
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The value of @code{errno} doesn't necessarily have to correspond to any
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of these macros, since some library functions might return other error
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codes of their own for other situations. The only values that are
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guaranteed to be meaningful for a particular library function are the
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ones that this manual lists for that function.
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Except on @gnuhurdsystems{}, almost any system call can return @code{EFAULT} if
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it is given an invalid pointer as an argument. Since this could only
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happen as a result of a bug in your program, and since it will not
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happen on @gnuhurdsystems{}, we have saved space by not mentioning
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@code{EFAULT} in the descriptions of individual functions.
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In some Unix systems, many system calls can also return @code{EFAULT} if
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given as an argument a pointer into the stack, and the kernel for some
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obscure reason fails in its attempt to extend the stack. If this ever
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happens, you should probably try using statically or dynamically
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allocated memory instead of stack memory on that system.
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@node Error Codes, Error Messages, Checking for Errors, Error Reporting
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@section Error Codes
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@pindex errno.h
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The error code macros are defined in the header file @file{errno.h}.
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All of them expand into integer constant values. Some of these error
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codes can't occur on @gnusystems{}, but they can occur using @theglibc{}
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on other systems.
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@deftypevr Macro int EPERM
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@standards{POSIX.1, errno.h}
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@errno{EPERM, 1, Operation not permitted}
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Only the owner of the file (or other resource)
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or processes with special privileges can perform the operation.
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@end deftypevr
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@deftypevr Macro int ENOENT
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@standards{POSIX.1, errno.h}
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@errno{ENOENT, 2, No such file or directory}
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This is a ``file doesn't exist'' error
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for ordinary files that are referenced in contexts where they are
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expected to already exist.
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@end deftypevr
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@deftypevr Macro int ESRCH
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@standards{POSIX.1, errno.h}
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@errno{ESRCH, 3, No such process}
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No process matches the specified process ID.
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@end deftypevr
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@deftypevr Macro int EINTR
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@standards{POSIX.1, errno.h}
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@errno{EINTR, 4, Interrupted system call}
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An asynchronous signal occurred and prevented
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completion of the call. When this happens, you should try the call
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again.
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You can choose to have functions resume after a signal that is handled,
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rather than failing with @code{EINTR}; see @ref{Interrupted
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Primitives}.
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@end deftypevr
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@deftypevr Macro int EIO
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@standards{POSIX.1, errno.h}
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@errno{EIO, 5, Input/output error}
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Usually used for physical read or write errors.
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@end deftypevr
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@deftypevr Macro int ENXIO
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@standards{POSIX.1, errno.h}
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@errno{ENXIO, 6, No such device or address}
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The system tried to use the device
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represented by a file you specified, and it couldn't find the device.
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This can mean that the device file was installed incorrectly, or that
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the physical device is missing or not correctly attached to the
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computer.
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@end deftypevr
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@deftypevr Macro int E2BIG
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@standards{POSIX.1, errno.h}
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@errno{E2BIG, 7, Argument list too long}
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Used when the arguments passed to a new program
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being executed with one of the @code{exec} functions (@pxref{Executing a
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File}) occupy too much memory space. This condition never arises on
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@gnuhurdsystems{}.
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@end deftypevr
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@deftypevr Macro int ENOEXEC
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@standards{POSIX.1, errno.h}
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@errno{ENOEXEC, 8, Exec format error}
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Invalid executable file format. This condition is detected by the
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@code{exec} functions; see @ref{Executing a File}.
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@end deftypevr
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@deftypevr Macro int EBADF
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@standards{POSIX.1, errno.h}
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@errno{EBADF, 9, Bad file descriptor}
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For example, I/O on a descriptor that has been
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closed or reading from a descriptor open only for writing (or vice
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versa).
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@end deftypevr
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@deftypevr Macro int ECHILD
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@standards{POSIX.1, errno.h}
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@errno{ECHILD, 10, No child processes}
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This error happens on operations that are
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supposed to manipulate child processes, when there aren't any processes
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to manipulate.
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@end deftypevr
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@deftypevr Macro int EDEADLK
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@standards{POSIX.1, errno.h}
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@errno{EDEADLK, 11, Resource deadlock avoided}
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Allocating a system resource would have resulted in a
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deadlock situation. The system does not guarantee that it will notice
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all such situations. This error means you got lucky and the system
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noticed; it might just hang. @xref{File Locks}, for an example.
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@end deftypevr
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@deftypevr Macro int ENOMEM
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@standards{POSIX.1, errno.h}
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@errno{ENOMEM, 12, Cannot allocate memory}
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The system cannot allocate more virtual memory
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because its capacity is full.
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@end deftypevr
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@deftypevr Macro int EACCES
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@standards{POSIX.1, errno.h}
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@errno{EACCES, 13, Permission denied}
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The file permissions do not allow the attempted operation.
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@end deftypevr
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@deftypevr Macro int EFAULT
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@standards{POSIX.1, errno.h}
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@errno{EFAULT, 14, Bad address}
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An invalid pointer was detected.
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On @gnuhurdsystems{}, this error never happens; you get a signal instead.
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@end deftypevr
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@deftypevr Macro int ENOTBLK
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@standards{BSD, errno.h}
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@errno{ENOTBLK, 15, Block device required}
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A file that isn't a block special file was given in a situation that
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requires one. For example, trying to mount an ordinary file as a file
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system in Unix gives this error.
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@end deftypevr
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@deftypevr Macro int EBUSY
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@standards{POSIX.1, errno.h}
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@errno{EBUSY, 16, Device or resource busy}
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A system resource that can't be shared is already in use.
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For example, if you try to delete a file that is the root of a currently
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mounted filesystem, you get this error.
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@end deftypevr
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@deftypevr Macro int EEXIST
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@standards{POSIX.1, errno.h}
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@errno{EEXIST, 17, File exists}
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An existing file was specified in a context where it only
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makes sense to specify a new file.
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@end deftypevr
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@deftypevr Macro int EXDEV
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@standards{POSIX.1, errno.h}
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@errno{EXDEV, 18, Invalid cross-device link}
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An attempt to make an improper link across file systems was detected.
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This happens not only when you use @code{link} (@pxref{Hard Links}) but
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also when you rename a file with @code{rename} (@pxref{Renaming Files}).
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@end deftypevr
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@deftypevr Macro int ENODEV
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@standards{POSIX.1, errno.h}
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@errno{ENODEV, 19, No such device}
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The wrong type of device was given to a function that expects a
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particular sort of device.
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@end deftypevr
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@deftypevr Macro int ENOTDIR
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@standards{POSIX.1, errno.h}
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@errno{ENOTDIR, 20, Not a directory}
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A file that isn't a directory was specified when a directory is required.
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@end deftypevr
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@deftypevr Macro int EISDIR
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@standards{POSIX.1, errno.h}
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@errno{EISDIR, 21, Is a directory}
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You cannot open a directory for writing,
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or create or remove hard links to it.
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@end deftypevr
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@deftypevr Macro int EINVAL
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@standards{POSIX.1, errno.h}
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@errno{EINVAL, 22, Invalid argument}
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This is used to indicate various kinds of problems
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with passing the wrong argument to a library function.
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@end deftypevr
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@deftypevr Macro int EMFILE
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@standards{POSIX.1, errno.h}
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@errno{EMFILE, 24, Too many open files}
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The current process has too many files open and can't open any more.
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Duplicate descriptors do count toward this limit.
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In BSD and GNU, the number of open files is controlled by a resource
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limit that can usually be increased. If you get this error, you might
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want to increase the @code{RLIMIT_NOFILE} limit or make it unlimited;
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@pxref{Limits on Resources}.
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@end deftypevr
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@deftypevr Macro int ENFILE
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@standards{POSIX.1, errno.h}
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@errno{ENFILE, 23, Too many open files in system}
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There are too many distinct file openings in the entire system. Note
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that any number of linked channels count as just one file opening; see
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@ref{Linked Channels}. This error never occurs on @gnuhurdsystems{}.
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@end deftypevr
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@deftypevr Macro int ENOTTY
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@standards{POSIX.1, errno.h}
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@errno{ENOTTY, 25, Inappropriate ioctl for device}
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Inappropriate I/O control operation, such as trying to set terminal
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modes on an ordinary file.
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@end deftypevr
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@deftypevr Macro int ETXTBSY
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@standards{BSD, errno.h}
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@errno{ETXTBSY, 26, Text file busy}
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An attempt to execute a file that is currently open for writing, or
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write to a file that is currently being executed. Often using a
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debugger to run a program is considered having it open for writing and
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will cause this error. (The name stands for ``text file busy''.) This
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is not an error on @gnuhurdsystems{}; the text is copied as necessary.
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@end deftypevr
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@deftypevr Macro int EFBIG
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@standards{POSIX.1, errno.h}
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@errno{EFBIG, 27, File too large}
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The size of a file would be larger than allowed by the system.
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@end deftypevr
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@deftypevr Macro int ENOSPC
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@standards{POSIX.1, errno.h}
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@errno{ENOSPC, 28, No space left on device}
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Write operation on a file failed because the
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disk is full.
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@end deftypevr
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@deftypevr Macro int ESPIPE
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@standards{POSIX.1, errno.h}
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@errno{ESPIPE, 29, Illegal seek}
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Invalid seek operation (such as on a pipe).
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@end deftypevr
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@deftypevr Macro int EROFS
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@standards{POSIX.1, errno.h}
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@errno{EROFS, 30, Read-only file system}
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An attempt was made to modify something on a read-only file system.
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@end deftypevr
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@deftypevr Macro int EMLINK
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@standards{POSIX.1, errno.h}
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@errno{EMLINK, 31, Too many links}
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The link count of a single file would become too large.
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@code{rename} can cause this error if the file being renamed already has
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as many links as it can take (@pxref{Renaming Files}).
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@end deftypevr
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@deftypevr Macro int EPIPE
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@standards{POSIX.1, errno.h}
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@errno{EPIPE, 32, Broken pipe}
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There is no process reading from the other end of a pipe.
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Every library function that returns this error code also generates a
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@code{SIGPIPE} signal; this signal terminates the program if not handled
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or blocked. Thus, your program will never actually see @code{EPIPE}
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unless it has handled or blocked @code{SIGPIPE}.
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@end deftypevr
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@deftypevr Macro int EDOM
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@standards{ISO, errno.h}
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@errno{EDOM, 33, Numerical argument out of domain}
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Used by mathematical functions when an argument value does
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not fall into the domain over which the function is defined.
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@end deftypevr
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@deftypevr Macro int ERANGE
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@standards{ISO, errno.h}
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@errno{ERANGE, 34, Numerical result out of range}
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Used by mathematical functions when the result value is
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not representable because of overflow or underflow.
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@end deftypevr
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@deftypevr Macro int EAGAIN
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@standards{POSIX.1, errno.h}
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@errno{EAGAIN, 35, Resource temporarily unavailable}
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|
The call might work if you try again
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later. The macro @code{EWOULDBLOCK} is another name for @code{EAGAIN};
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they are always the same in @theglibc{}.
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This error can happen in a few different situations:
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@itemize @bullet
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@item
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An operation that would block was attempted on an object that has
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non-blocking mode selected. Trying the same operation again will block
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|
until some external condition makes it possible to read, write, or
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connect (whatever the operation). You can use @code{select} to find out
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|
when the operation will be possible; @pxref{Waiting for I/O}.
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|
|
@strong{Portability Note:} In many older Unix systems, this condition
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|
was indicated by @code{EWOULDBLOCK}, which was a distinct error code
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|
different from @code{EAGAIN}. To make your program portable, you should
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check for both codes and treat them the same.
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|
|
@item
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A temporary resource shortage made an operation impossible. @code{fork}
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can return this error. It indicates that the shortage is expected to
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pass, so your program can try the call again later and it may succeed.
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It is probably a good idea to delay for a few seconds before trying it
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again, to allow time for other processes to release scarce resources.
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Such shortages are usually fairly serious and affect the whole system,
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so usually an interactive program should report the error to the user
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and return to its command loop.
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@end itemize
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@end deftypevr
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@deftypevr Macro int EWOULDBLOCK
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@standards{BSD, errno.h}
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@errno{EWOULDBLOCK, EAGAIN, Operation would block}
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In @theglibc{}, this is another name for @code{EAGAIN} (above).
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The values are always the same, on every operating system.
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C libraries in many older Unix systems have @code{EWOULDBLOCK} as a
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separate error code.
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@end deftypevr
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@deftypevr Macro int EINPROGRESS
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@standards{BSD, errno.h}
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@errno{EINPROGRESS, 36, Operation now in progress}
|
|
An operation that cannot complete immediately was initiated on an object
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|
that has non-blocking mode selected. Some functions that must always
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|
block (such as @code{connect}; @pxref{Connecting}) never return
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@code{EAGAIN}. Instead, they return @code{EINPROGRESS} to indicate that
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the operation has begun and will take some time. Attempts to manipulate
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the object before the call completes return @code{EALREADY}. You can
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use the @code{select} function to find out when the pending operation
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has completed; @pxref{Waiting for I/O}.
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@end deftypevr
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@deftypevr Macro int EALREADY
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@standards{BSD, errno.h}
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@errno{EALREADY, 37, Operation already in progress}
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|
An operation is already in progress on an object that has non-blocking
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mode selected.
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@end deftypevr
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@deftypevr Macro int ENOTSOCK
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@standards{BSD, errno.h}
|
|
@errno{ENOTSOCK, 38, Socket operation on non-socket}
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|
A file that isn't a socket was specified when a socket is required.
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@end deftypevr
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@deftypevr Macro int EMSGSIZE
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@standards{BSD, errno.h}
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@errno{EMSGSIZE, 40, Message too long}
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The size of a message sent on a socket was larger than the supported
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maximum size.
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@end deftypevr
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@deftypevr Macro int EPROTOTYPE
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@standards{BSD, errno.h}
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@errno{EPROTOTYPE, 41, Protocol wrong type for socket}
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|
The socket type does not support the requested communications protocol.
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@end deftypevr
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@deftypevr Macro int ENOPROTOOPT
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|
@standards{BSD, errno.h}
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|
@errno{ENOPROTOOPT, 42, Protocol not available}
|
|
You specified a socket option that doesn't make sense for the
|
|
particular protocol being used by the socket. @xref{Socket Options}.
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int EPROTONOSUPPORT
|
|
@standards{BSD, errno.h}
|
|
@errno{EPROTONOSUPPORT, 43, Protocol not supported}
|
|
The socket domain does not support the requested communications protocol
|
|
(perhaps because the requested protocol is completely invalid).
|
|
@xref{Creating a Socket}.
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int ESOCKTNOSUPPORT
|
|
@standards{BSD, errno.h}
|
|
@errno{ESOCKTNOSUPPORT, 44, Socket type not supported}
|
|
The socket type is not supported.
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int EOPNOTSUPP
|
|
@standards{BSD, errno.h}
|
|
@errno{EOPNOTSUPP, 45, Operation not supported}
|
|
The operation you requested is not supported. Some socket functions
|
|
don't make sense for all types of sockets, and others may not be
|
|
implemented for all communications protocols. On @gnuhurdsystems{}, this
|
|
error can happen for many calls when the object does not support the
|
|
particular operation; it is a generic indication that the server knows
|
|
nothing to do for that call.
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int EPFNOSUPPORT
|
|
@standards{BSD, errno.h}
|
|
@errno{EPFNOSUPPORT, 46, Protocol family not supported}
|
|
The socket communications protocol family you requested is not supported.
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int EAFNOSUPPORT
|
|
@standards{BSD, errno.h}
|
|
@errno{EAFNOSUPPORT, 47, Address family not supported by protocol}
|
|
The address family specified for a socket is not supported; it is
|
|
inconsistent with the protocol being used on the socket. @xref{Sockets}.
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int EADDRINUSE
|
|
@standards{BSD, errno.h}
|
|
@errno{EADDRINUSE, 48, Address already in use}
|
|
The requested socket address is already in use. @xref{Socket Addresses}.
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int EADDRNOTAVAIL
|
|
@standards{BSD, errno.h}
|
|
@errno{EADDRNOTAVAIL, 49, Cannot assign requested address}
|
|
The requested socket address is not available; for example, you tried
|
|
to give a socket a name that doesn't match the local host name.
|
|
@xref{Socket Addresses}.
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int ENETDOWN
|
|
@standards{BSD, errno.h}
|
|
@errno{ENETDOWN, 50, Network is down}
|
|
A socket operation failed because the network was down.
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int ENETUNREACH
|
|
@standards{BSD, errno.h}
|
|
@errno{ENETUNREACH, 51, Network is unreachable}
|
|
A socket operation failed because the subnet containing the remote host
|
|
was unreachable.
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int ENETRESET
|
|
@standards{BSD, errno.h}
|
|
@errno{ENETRESET, 52, Network dropped connection on reset}
|
|
A network connection was reset because the remote host crashed.
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int ECONNABORTED
|
|
@standards{BSD, errno.h}
|
|
@errno{ECONNABORTED, 53, Software caused connection abort}
|
|
A network connection was aborted locally.
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int ECONNRESET
|
|
@standards{BSD, errno.h}
|
|
@errno{ECONNRESET, 54, Connection reset by peer}
|
|
A network connection was closed for reasons outside the control of the
|
|
local host, such as by the remote machine rebooting or an unrecoverable
|
|
protocol violation.
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int ENOBUFS
|
|
@standards{BSD, errno.h}
|
|
@errno{ENOBUFS, 55, No buffer space available}
|
|
The kernel's buffers for I/O operations are all in use. In GNU, this
|
|
error is always synonymous with @code{ENOMEM}; you may get one or the
|
|
other from network operations.
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int EISCONN
|
|
@standards{BSD, errno.h}
|
|
@errno{EISCONN, 56, Transport endpoint is already connected}
|
|
You tried to connect a socket that is already connected.
|
|
@xref{Connecting}.
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int ENOTCONN
|
|
@standards{BSD, errno.h}
|
|
@errno{ENOTCONN, 57, Transport endpoint is not connected}
|
|
The socket is not connected to anything. You get this error when you
|
|
try to transmit data over a socket, without first specifying a
|
|
destination for the data. For a connectionless socket (for datagram
|
|
protocols, such as UDP), you get @code{EDESTADDRREQ} instead.
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int EDESTADDRREQ
|
|
@standards{BSD, errno.h}
|
|
@errno{EDESTADDRREQ, 39, Destination address required}
|
|
No default destination address was set for the socket. You get this
|
|
error when you try to transmit data over a connectionless socket,
|
|
without first specifying a destination for the data with @code{connect}.
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int ESHUTDOWN
|
|
@standards{BSD, errno.h}
|
|
@errno{ESHUTDOWN, 58, Cannot send after transport endpoint shutdown}
|
|
The socket has already been shut down.
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int ETOOMANYREFS
|
|
@standards{BSD, errno.h}
|
|
@errno{ETOOMANYREFS, 59, Too many references: cannot splice}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int ETIMEDOUT
|
|
@standards{BSD, errno.h}
|
|
@errno{ETIMEDOUT, 60, Connection timed out}
|
|
A socket operation with a specified timeout received no response during
|
|
the timeout period.
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int ECONNREFUSED
|
|
@standards{BSD, errno.h}
|
|
@errno{ECONNREFUSED, 61, Connection refused}
|
|
A remote host refused to allow the network connection (typically because
|
|
it is not running the requested service).
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int ELOOP
|
|
@standards{BSD, errno.h}
|
|
@errno{ELOOP, 62, Too many levels of symbolic links}
|
|
Too many levels of symbolic links were encountered in looking up a file name.
|
|
This often indicates a cycle of symbolic links.
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int ENAMETOOLONG
|
|
@standards{POSIX.1, errno.h}
|
|
@errno{ENAMETOOLONG, 63, File name too long}
|
|
Filename too long (longer than @code{PATH_MAX}; @pxref{Limits for
|
|
Files}) or host name too long (in @code{gethostname} or
|
|
@code{sethostname}; @pxref{Host Identification}).
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int EHOSTDOWN
|
|
@standards{BSD, errno.h}
|
|
@errno{EHOSTDOWN, 64, Host is down}
|
|
The remote host for a requested network connection is down.
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int EHOSTUNREACH
|
|
@standards{BSD, errno.h}
|
|
@errno{EHOSTUNREACH, 65, No route to host}
|
|
The remote host for a requested network connection is not reachable.
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int ENOTEMPTY
|
|
@standards{POSIX.1, errno.h}
|
|
@errno{ENOTEMPTY, 66, Directory not empty}
|
|
Directory not empty, where an empty directory was expected. Typically,
|
|
this error occurs when you are trying to delete a directory.
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int EPROCLIM
|
|
@standards{BSD, errno.h}
|
|
@errno{EPROCLIM, 67, Too many processes}
|
|
This means that the per-user limit on new process would be exceeded by
|
|
an attempted @code{fork}. @xref{Limits on Resources}, for details on
|
|
the @code{RLIMIT_NPROC} limit.
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int EUSERS
|
|
@standards{BSD, errno.h}
|
|
@errno{EUSERS, 68, Too many users}
|
|
The file quota system is confused because there are too many users.
|
|
@c This can probably happen in a GNU system when using NFS.
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int EDQUOT
|
|
@standards{BSD, errno.h}
|
|
@errno{EDQUOT, 69, Disk quota exceeded}
|
|
The user's disk quota was exceeded.
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int ESTALE
|
|
@standards{BSD, errno.h}
|
|
@errno{ESTALE, 70, Stale file handle}
|
|
This indicates an internal confusion in the
|
|
file system which is due to file system rearrangements on the server host
|
|
for NFS file systems or corruption in other file systems.
|
|
Repairing this condition usually requires unmounting, possibly repairing
|
|
and remounting the file system.
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int EREMOTE
|
|
@standards{BSD, errno.h}
|
|
@errno{EREMOTE, 71, Object is remote}
|
|
An attempt was made to NFS-mount a remote file system with a file name that
|
|
already specifies an NFS-mounted file.
|
|
(This is an error on some operating systems, but we expect it to work
|
|
properly on @gnuhurdsystems{}, making this error code impossible.)
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int EBADRPC
|
|
@standards{BSD, errno.h}
|
|
@errno{EBADRPC, 72, RPC struct is bad}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int ERPCMISMATCH
|
|
@standards{BSD, errno.h}
|
|
@errno{ERPCMISMATCH, 73, RPC version wrong}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int EPROGUNAVAIL
|
|
@standards{BSD, errno.h}
|
|
@errno{EPROGUNAVAIL, 74, RPC program not available}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int EPROGMISMATCH
|
|
@standards{BSD, errno.h}
|
|
@errno{EPROGMISMATCH, 75, RPC program version wrong}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int EPROCUNAVAIL
|
|
@standards{BSD, errno.h}
|
|
@errno{EPROCUNAVAIL, 76, RPC bad procedure for program}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int ENOLCK
|
|
@standards{POSIX.1, errno.h}
|
|
@errno{ENOLCK, 77, No locks available}
|
|
This is used by the file locking facilities; see
|
|
@ref{File Locks}. This error is never generated by @gnuhurdsystems{}, but
|
|
it can result from an operation to an NFS server running another
|
|
operating system.
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int EFTYPE
|
|
@standards{BSD, errno.h}
|
|
@errno{EFTYPE, 79, Inappropriate file type or format}
|
|
The file was the wrong type for the
|
|
operation, or a data file had the wrong format.
|
|
|
|
On some systems @code{chmod} returns this error if you try to set the
|
|
sticky bit on a non-directory file; @pxref{Setting Permissions}.
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int EAUTH
|
|
@standards{BSD, errno.h}
|
|
@errno{EAUTH, 80, Authentication error}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int ENEEDAUTH
|
|
@standards{BSD, errno.h}
|
|
@errno{ENEEDAUTH, 81, Need authenticator}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int ENOSYS
|
|
@standards{POSIX.1, errno.h}
|
|
@errno{ENOSYS, 78, Function not implemented}
|
|
This indicates that the function called is
|
|
not implemented at all, either in the C library itself or in the
|
|
operating system. When you get this error, you can be sure that this
|
|
particular function will always fail with @code{ENOSYS} unless you
|
|
install a new version of the C library or the operating system.
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int ELIBEXEC
|
|
@standards{GNU, errno.h}
|
|
@errno{ELIBEXEC, 83, Cannot exec a shared library directly}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int ENOTSUP
|
|
@standards{POSIX.1, errno.h}
|
|
@errno{ENOTSUP, 118, Not supported}
|
|
A function returns this error when certain parameter
|
|
values are valid, but the functionality they request is not available.
|
|
This can mean that the function does not implement a particular command
|
|
or option value or flag bit at all. For functions that operate on some
|
|
object given in a parameter, such as a file descriptor or a port, it
|
|
might instead mean that only @emph{that specific object} (file
|
|
descriptor, port, etc.) is unable to support the other parameters given;
|
|
different file descriptors might support different ranges of parameter
|
|
values.
|
|
|
|
If the entire function is not available at all in the implementation,
|
|
it returns @code{ENOSYS} instead.
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int EILSEQ
|
|
@standards{ISO, errno.h}
|
|
@errno{EILSEQ, 106, Invalid or incomplete multibyte or wide character}
|
|
While decoding a multibyte character the function came along an invalid
|
|
or an incomplete sequence of bytes or the given wide character is invalid.
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int EBACKGROUND
|
|
@standards{GNU, errno.h}
|
|
@errno{EBACKGROUND, 100, Inappropriate operation for background process}
|
|
On @gnuhurdsystems{}, servers supporting the @code{term} protocol return
|
|
this error for certain operations when the caller is not in the
|
|
foreground process group of the terminal. Users do not usually see this
|
|
error because functions such as @code{read} and @code{write} translate
|
|
it into a @code{SIGTTIN} or @code{SIGTTOU} signal. @xref{Job Control},
|
|
for information on process groups and these signals.
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int EDIED
|
|
@standards{GNU, errno.h}
|
|
@errno{EDIED, 101, Translator died}
|
|
On @gnuhurdsystems{}, opening a file returns this error when the file is
|
|
translated by a program and the translator program dies while starting
|
|
up, before it has connected to the file.
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int ED
|
|
@standards{GNU, errno.h}
|
|
@errno{ED, 102, ?}
|
|
The experienced user will know what is wrong.
|
|
@c This error code is a joke. Its perror text is part of the joke.
|
|
@c Don't change it.
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int EGREGIOUS
|
|
@standards{GNU, errno.h}
|
|
@errno{EGREGIOUS, 103, You really blew it this time}
|
|
You did @strong{what}?
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int EIEIO
|
|
@standards{GNU, errno.h}
|
|
@errno{EIEIO, 104, Computer bought the farm}
|
|
Go home and have a glass of warm, dairy-fresh milk.
|
|
@c Okay. Since you are dying to know, I'll tell you.
|
|
@c This is a joke, obviously. There is a children's song which begins,
|
|
@c "Old McDonald had a farm, e-i-e-i-o." Every time I see the (real)
|
|
@c errno macro EIO, I think about that song. Probably most of my
|
|
@c compatriots who program on Unix do, too. One of them must have stayed
|
|
@c up a little too late one night and decided to add it to Hurd or Glibc.
|
|
@c Whoever did it should be castigated, but it made me laugh.
|
|
@c --jtobey@channel1.com
|
|
@c
|
|
@c "bought the farm" means "died". -jtobey
|
|
@c
|
|
@c Translators, please do not translate this litteraly, translate it into
|
|
@c an idiomatic funny way of saying that the computer died.
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int EGRATUITOUS
|
|
@standards{GNU, errno.h}
|
|
@errno{EGRATUITOUS, 105, Gratuitous error}
|
|
This error code has no purpose.
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int EBADMSG
|
|
@standards{XOPEN, errno.h}
|
|
@errno{EBADMSG, 107, Bad message}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int EIDRM
|
|
@standards{XOPEN, errno.h}
|
|
@errno{EIDRM, 108, Identifier removed}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int EMULTIHOP
|
|
@standards{XOPEN, errno.h}
|
|
@errno{EMULTIHOP, 109, Multihop attempted}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int ENODATA
|
|
@standards{XOPEN, errno.h}
|
|
@errno{ENODATA, 110, No data available}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int ENOLINK
|
|
@standards{XOPEN, errno.h}
|
|
@errno{ENOLINK, 111, Link has been severed}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int ENOMSG
|
|
@standards{XOPEN, errno.h}
|
|
@errno{ENOMSG, 112, No message of desired type}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int ENOSR
|
|
@standards{XOPEN, errno.h}
|
|
@errno{ENOSR, 113, Out of streams resources}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int ENOSTR
|
|
@standards{XOPEN, errno.h}
|
|
@errno{ENOSTR, 114, Device not a stream}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int EOVERFLOW
|
|
@standards{XOPEN, errno.h}
|
|
@errno{EOVERFLOW, 115, Value too large for defined data type}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int EPROTO
|
|
@standards{XOPEN, errno.h}
|
|
@errno{EPROTO, 116, Protocol error}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int ETIME
|
|
@standards{XOPEN, errno.h}
|
|
@errno{ETIME, 117, Timer expired}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int ECANCELED
|
|
@standards{POSIX.1, errno.h}
|
|
@errno{ECANCELED, 119, Operation canceled}
|
|
An asynchronous operation was canceled before it
|
|
completed. @xref{Asynchronous I/O}. When you call @code{aio_cancel},
|
|
the normal result is for the operations affected to complete with this
|
|
error; @pxref{Cancel AIO Operations}.
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int EOWNERDEAD
|
|
@standards{GNU, errno.h}
|
|
@errno{EOWNERDEAD, 120, Owner died}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int ENOTRECOVERABLE
|
|
@standards{GNU, errno.h}
|
|
@errno{ENOTRECOVERABLE, 121, State not recoverable}
|
|
@end deftypevr
|
|
|
|
|
|
@emph{The following error codes are defined by the Linux/i386 kernel.
|
|
They are not yet documented.}
|
|
|
|
@deftypevr Macro int ERESTART
|
|
@standards{Linux???, errno.h}
|
|
@errno{ERESTART, ???/85, Interrupted system call should be restarted}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int ECHRNG
|
|
@standards{Linux???, errno.h}
|
|
@errno{ECHRNG, ???/44, Channel number out of range}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int EL2NSYNC
|
|
@standards{Obsolete, errno.h}
|
|
@errno{EL2NSYNC, ???/45, Level 2 not synchronized}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int EL3HLT
|
|
@standards{Obsolete, errno.h}
|
|
@errno{EL3HLT, ???/46, Level 3 halted}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int EL3RST
|
|
@standards{Obsolete, errno.h}
|
|
@errno{EL3RST, ???/47, Level 3 reset}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int ELNRNG
|
|
@standards{Linux???, errno.h}
|
|
@errno{ELNRNG, ???/48, Link number out of range}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int EUNATCH
|
|
@standards{Linux???, errno.h}
|
|
@errno{EUNATCH, ???/49, Protocol driver not attached}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int ENOCSI
|
|
@standards{Linux???, errno.h}
|
|
@errno{ENOCSI, ???/50, No CSI structure available}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int EL2HLT
|
|
@standards{Obsolete, errno.h}
|
|
@errno{EL2HLT, ???/51, Level 2 halted}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int EBADE
|
|
@standards{Linux???, errno.h}
|
|
@errno{EBADE, ???/52, Invalid exchange}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int EBADR
|
|
@standards{Linux???, errno.h}
|
|
@errno{EBADR, ???/53, Invalid request descriptor}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int EXFULL
|
|
@standards{Linux???, errno.h}
|
|
@errno{EXFULL, ???/54, Exchange full}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int ENOANO
|
|
@standards{Linux???, errno.h}
|
|
@errno{ENOANO, ???/55, No anode}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int EBADRQC
|
|
@standards{Linux???, errno.h}
|
|
@errno{EBADRQC, ???/56, Invalid request code}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int EBADSLT
|
|
@standards{Linux???, errno.h}
|
|
@errno{EBADSLT, ???/57, Invalid slot}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int EDEADLOCK
|
|
@standards{Linux???, errno.h}
|
|
@errno{EDEADLOCK, ???/58, File locking deadlock error}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int EBFONT
|
|
@standards{Linux???, errno.h}
|
|
@errno{EBFONT, ???/59, Bad font file format}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int ENONET
|
|
@standards{Linux???, errno.h}
|
|
@errno{ENONET, ???/64, Machine is not on the network}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int ENOPKG
|
|
@standards{Linux???, errno.h}
|
|
@errno{ENOPKG, ???/65, Package not installed}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int EADV
|
|
@standards{Linux???, errno.h}
|
|
@errno{EADV, ???/68, Advertise error}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int ESRMNT
|
|
@standards{Linux???, errno.h}
|
|
@errno{ESRMNT, ???/69, Srmount error}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int ECOMM
|
|
@standards{Linux???, errno.h}
|
|
@errno{ECOMM, ???/70, Communication error on send}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int EDOTDOT
|
|
@standards{Linux???, errno.h}
|
|
@errno{EDOTDOT, ???/73, RFS specific error}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int ENOTUNIQ
|
|
@standards{Linux???, errno.h}
|
|
@errno{ENOTUNIQ, ???/76, Name not unique on network}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int EBADFD
|
|
@standards{Linux???, errno.h}
|
|
@errno{EBADFD, ???/77, File descriptor in bad state}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int EREMCHG
|
|
@standards{Linux???, errno.h}
|
|
@errno{EREMCHG, ???/78, Remote address changed}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int ELIBACC
|
|
@standards{Linux???, errno.h}
|
|
@errno{ELIBACC, ???/79, Can not access a needed shared library}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int ELIBBAD
|
|
@standards{Linux???, errno.h}
|
|
@errno{ELIBBAD, ???/80, Accessing a corrupted shared library}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int ELIBSCN
|
|
@standards{Linux???, errno.h}
|
|
@errno{ELIBSCN, ???/81, .lib section in a.out corrupted}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int ELIBMAX
|
|
@standards{Linux???, errno.h}
|
|
@errno{ELIBMAX, ???/82, Attempting to link in too many shared libraries}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int ESTRPIPE
|
|
@standards{Linux???, errno.h}
|
|
@errno{ESTRPIPE, ???/86, Streams pipe error}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int EUCLEAN
|
|
@standards{Linux???, errno.h}
|
|
@errno{EUCLEAN, ???/117, Structure needs cleaning}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int ENOTNAM
|
|
@standards{Linux???, errno.h}
|
|
@errno{ENOTNAM, ???/118, Not a XENIX named type file}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int ENAVAIL
|
|
@standards{Linux???, errno.h}
|
|
@errno{ENAVAIL, ???/119, No XENIX semaphores available}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int EISNAM
|
|
@standards{Linux???, errno.h}
|
|
@errno{EISNAM, ???/120, Is a named type file}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int EREMOTEIO
|
|
@standards{Linux???, errno.h}
|
|
@errno{EREMOTEIO, ???/121, Remote I/O error}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int ENOMEDIUM
|
|
@standards{Linux???, errno.h}
|
|
@errno{ENOMEDIUM, ???/???, No medium found}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int EMEDIUMTYPE
|
|
@standards{Linux???, errno.h}
|
|
@errno{EMEDIUMTYPE, ???/???, Wrong medium type}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int ENOKEY
|
|
@standards{Linux, errno.h}
|
|
@errno{ENOKEY, ???/???, Required key not available}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int EKEYEXPIRED
|
|
@standards{Linux, errno.h}
|
|
@errno{EKEYEXPIRED, ???/???, Key has expired}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int EKEYREVOKED
|
|
@standards{Linux, errno.h}
|
|
@errno{EKEYREVOKED, ???/???, Key has been revoked}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int EKEYREJECTED
|
|
@standards{Linux, errno.h}
|
|
@errno{EKEYREJECTED, ???/???, Key was rejected by service}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int ERFKILL
|
|
@standards{Linux, errno.h}
|
|
@errno{ERFKILL, ???/???, Operation not possible due to RF-kill}
|
|
@end deftypevr
|
|
|
|
@deftypevr Macro int EHWPOISON
|
|
@standards{Linux, errno.h}
|
|
@errno{EHWPOISON, ???/???, Memory page has hardware error}
|
|
@end deftypevr
|
|
|
|
@node Error Messages, , Error Codes, Error Reporting
|
|
@section Error Messages
|
|
|
|
The library has functions and variables designed to make it easy for
|
|
your program to report informative error messages in the customary
|
|
format about the failure of a library call. The functions
|
|
@code{strerror} and @code{perror} give you the standard error message
|
|
for a given error code; the variable
|
|
@w{@code{program_invocation_short_name}} gives you convenient access to the
|
|
name of the program that encountered the error.
|
|
|
|
@deftypefun {char *} strerror (int @var{errnum})
|
|
@standards{ISO, string.h}
|
|
@safety{@prelim{}@mtunsafe{@mtasurace{:strerror}}@asunsafe{@ascuheap{} @ascuintl{}}@acunsafe{@acsmem{}}}
|
|
@c Calls strerror_r with a static buffer allocated with malloc on the
|
|
@c first use.
|
|
The @code{strerror} function maps the error code (@pxref{Checking for
|
|
Errors}) specified by the @var{errnum} argument to a descriptive error
|
|
message string. The return value is a pointer to this string.
|
|
|
|
The value @var{errnum} normally comes from the variable @code{errno}.
|
|
|
|
You should not modify the string returned by @code{strerror}. Also, if
|
|
you make subsequent calls to @code{strerror}, the string might be
|
|
overwritten. (But it's guaranteed that no library function ever calls
|
|
@code{strerror} behind your back.)
|
|
|
|
The function @code{strerror} is declared in @file{string.h}.
|
|
@end deftypefun
|
|
|
|
@deftypefun {char *} strerror_r (int @var{errnum}, char *@var{buf}, size_t @var{n})
|
|
@standards{GNU, string.h}
|
|
@safety{@prelim{}@mtsafe{}@asunsafe{@ascuintl{}}@acunsafe{}}
|
|
The @code{strerror_r} function works like @code{strerror} but instead of
|
|
returning the error message in a statically allocated buffer shared by
|
|
all threads in the process, it returns a private copy for the
|
|
thread. This might be either some permanent global data or a message
|
|
string in the user supplied buffer starting at @var{buf} with the
|
|
length of @var{n} bytes.
|
|
|
|
At most @var{n} characters are written (including the NUL byte) so it is
|
|
up to the user to select a buffer large enough.
|
|
|
|
This function should always be used in multi-threaded programs since
|
|
there is no way to guarantee the string returned by @code{strerror}
|
|
really belongs to the last call of the current thread.
|
|
|
|
The function @code{strerror_r} is a GNU extension and it is declared in
|
|
@file{string.h}.
|
|
@end deftypefun
|
|
|
|
@deftypefun void perror (const char *@var{message})
|
|
@standards{ISO, stdio.h}
|
|
@safety{@prelim{}@mtsafe{@mtasurace{:stderr}}@asunsafe{@asucorrupt{} @ascuintl{} @ascuheap{} @asulock{}}@acunsafe{@acucorrupt{} @aculock{} @acsmem{} @acsfd{}}}
|
|
@c Besides strerror_r's and some of fprintf's issues, if stderr is not
|
|
@c oriented yet, create a new stream with a dup of stderr's fd and write
|
|
@c to that instead of stderr, to avoid orienting it.
|
|
This function prints an error message to the stream @code{stderr};
|
|
see @ref{Standard Streams}. The orientation of @code{stderr} is not
|
|
changed.
|
|
|
|
If you call @code{perror} with a @var{message} that is either a null
|
|
pointer or an empty string, @code{perror} just prints the error message
|
|
corresponding to @code{errno}, adding a trailing newline.
|
|
|
|
If you supply a non-null @var{message} argument, then @code{perror}
|
|
prefixes its output with this string. It adds a colon and a space
|
|
character to separate the @var{message} from the error string corresponding
|
|
to @code{errno}.
|
|
|
|
The function @code{perror} is declared in @file{stdio.h}.
|
|
@end deftypefun
|
|
|
|
@deftypefun {const char *} strerrorname_np (int @var{errnum})
|
|
@standards{GNU, string.h}
|
|
@safety{@mtsafe{}@assafe{}@acsafe{}}
|
|
This function returns the name describing the error @var{errnum} or
|
|
@code{NULL} if there is no known constant with this value (e.g "EINVAL"
|
|
for @code{EINVAL}).
|
|
|
|
@pindex string.h
|
|
This function is a GNU extension, declared in the header file @file{string.h}.
|
|
@end deftypefun
|
|
|
|
@deftypefun {const char *} strerrordesc_np (int @var{errnum})
|
|
@standards{GNU, string.h}
|
|
@safety{@mtsafe{}@assafe{}@acsafe{}}
|
|
This function returns the message describing the error @var{errnum} or
|
|
@code{NULL} if there is no known constant with this value (e.g "Invalid
|
|
argument" for @code{EINVAL}). Different than @code{strerror} the returned
|
|
description is not translated.
|
|
|
|
@pindex string.h
|
|
This function is a GNU extension, declared in the header file @file{string.h}.
|
|
@end deftypefun
|
|
|
|
@code{strerror} and @code{perror} produce the exact same message for any
|
|
given error code; the precise text varies from system to system. With
|
|
@theglibc{}, the messages are fairly short; there are no multi-line
|
|
messages or embedded newlines. Each error message begins with a capital
|
|
letter and does not include any terminating punctuation.
|
|
|
|
@cindex program name
|
|
@cindex name of running program
|
|
Many programs that don't read input from the terminal are designed to
|
|
exit if any system call fails. By convention, the error message from
|
|
such a program should start with the program's name, sans directories.
|
|
You can find that name in the variable
|
|
@code{program_invocation_short_name}; the full file name is stored the
|
|
variable @code{program_invocation_name}.
|
|
|
|
@deftypevar {char *} program_invocation_name
|
|
@standards{GNU, errno.h}
|
|
This variable's value is the name that was used to invoke the program
|
|
running in the current process. It is the same as @code{argv[0]}. Note
|
|
that this is not necessarily a useful file name; often it contains no
|
|
directory names. @xref{Program Arguments}.
|
|
|
|
This variable is a GNU extension and is declared in @file{errno.h}.
|
|
@end deftypevar
|
|
|
|
@deftypevar {char *} program_invocation_short_name
|
|
@standards{GNU, errno.h}
|
|
This variable's value is the name that was used to invoke the program
|
|
running in the current process, with directory names removed. (That is
|
|
to say, it is the same as @code{program_invocation_name} minus
|
|
everything up to the last slash, if any.)
|
|
|
|
This variable is a GNU extension and is declared in @file{errno.h}.
|
|
@end deftypevar
|
|
|
|
The library initialization code sets up both of these variables before
|
|
calling @code{main}.
|
|
|
|
@strong{Portability Note:} If you want your program to work with
|
|
non-GNU libraries, you must save the value of @code{argv[0]} in
|
|
@code{main}, and then strip off the directory names yourself. We
|
|
added these extensions to make it possible to write self-contained
|
|
error-reporting subroutines that require no explicit cooperation from
|
|
@code{main}.
|
|
|
|
Here is an example showing how to handle failure to open a file
|
|
correctly. The function @code{open_sesame} tries to open the named file
|
|
for reading and returns a stream if successful. The @code{fopen}
|
|
library function returns a null pointer if it couldn't open the file for
|
|
some reason. In that situation, @code{open_sesame} constructs an
|
|
appropriate error message using the @code{strerror} function, and
|
|
terminates the program. If we were going to make some other library
|
|
calls before passing the error code to @code{strerror}, we'd have to
|
|
save it in a local variable instead, because those other library
|
|
functions might overwrite @code{errno} in the meantime.
|
|
|
|
@smallexample
|
|
#define _GNU_SOURCE
|
|
|
|
#include <errno.h>
|
|
#include <stdio.h>
|
|
#include <stdlib.h>
|
|
#include <string.h>
|
|
|
|
FILE *
|
|
open_sesame (char *name)
|
|
@{
|
|
FILE *stream;
|
|
|
|
errno = 0;
|
|
stream = fopen (name, "r");
|
|
if (stream == NULL)
|
|
@{
|
|
fprintf (stderr, "%s: Couldn't open file %s; %s\n",
|
|
program_invocation_short_name, name, strerror (errno));
|
|
exit (EXIT_FAILURE);
|
|
@}
|
|
else
|
|
return stream;
|
|
@}
|
|
@end smallexample
|
|
|
|
Using @code{perror} has the advantage that the function is portable and
|
|
available on all systems implementing @w{ISO C}. But often the text
|
|
@code{perror} generates is not what is wanted and there is no way to
|
|
extend or change what @code{perror} does. The GNU coding standard, for
|
|
instance, requires error messages to be preceded by the program name and
|
|
programs which read some input files should provide information
|
|
about the input file name and the line number in case an error is
|
|
encountered while reading the file. For these occasions there are two
|
|
functions available which are widely used throughout the GNU project.
|
|
These functions are declared in @file{error.h}.
|
|
|
|
@deftypefun void error (int @var{status}, int @var{errnum}, const char *@var{format}, @dots{})
|
|
@standards{GNU, error.h}
|
|
@safety{@prelim{}@mtsafe{@mtslocale{}}@asunsafe{@asucorrupt{} @asuheap{} @asuintl{}}@acsafe{}}
|
|
@c Cancellation is disabled throughout the execution. It flushes stdout
|
|
@c and then holds a lock on stderr while printing the program name and
|
|
@c then running error_tail. The non-wide case just runs vfprintf; the
|
|
@c wide case converts the message to an alloca/malloc-allocated buffer
|
|
@c with mbsrtowcs, then prints it with vfwprintf. Afterwards,
|
|
@c print_errno_message calls strerror_r and fxprintf.
|
|
The @code{error} function can be used to report general problems during
|
|
program execution. The @var{format} argument is a format string just
|
|
like those given to the @code{printf} family of functions. The
|
|
arguments required for the format can follow the @var{format} parameter.
|
|
Just like @code{perror}, @code{error} also can report an error code in
|
|
textual form. But unlike @code{perror} the error value is explicitly
|
|
passed to the function in the @var{errnum} parameter. This eliminates
|
|
the problem mentioned above that the error reporting function must be
|
|
called immediately after the function causing the error since otherwise
|
|
@code{errno} might have a different value.
|
|
|
|
@code{error} prints first the program name. If the application
|
|
defined a global variable @code{error_print_progname} and points it to a
|
|
function this function will be called to print the program name.
|
|
Otherwise the string from the global variable @code{program_name} is
|
|
used. The program name is followed by a colon and a space which in turn
|
|
is followed by the output produced by the format string. If the
|
|
@var{errnum} parameter is non-zero the format string output is followed
|
|
by a colon and a space, followed by the error message for the error code
|
|
@var{errnum}. In any case is the output terminated with a newline.
|
|
|
|
The output is directed to the @code{stderr} stream. If the
|
|
@code{stderr} wasn't oriented before the call it will be narrow-oriented
|
|
afterwards.
|
|
|
|
The function will return unless the @var{status} parameter has a
|
|
non-zero value. In this case the function will call @code{exit} with
|
|
the @var{status} value for its parameter and therefore never return. If
|
|
@code{error} returns, the global variable @code{error_message_count} is
|
|
incremented by one to keep track of the number of errors reported.
|
|
@end deftypefun
|
|
|
|
@deftypefun void error_at_line (int @var{status}, int @var{errnum}, const char *@var{fname}, unsigned int @var{lineno}, const char *@var{format}, @dots{})
|
|
@standards{GNU, error.h}
|
|
@safety{@prelim{}@mtunsafe{@mtasurace{:error_at_line/error_one_per_line} @mtslocale{}}@asunsafe{@asucorrupt{} @asuheap{} @asuintl{}}@acunsafe{@acucorrupt{/error_one_per_line}}}
|
|
@c The error_one_per_line variable is accessed (without any form of
|
|
@c synchronization, but since it's an int used once, it should be safe
|
|
@c enough) and, if this mode is enabled, static variables used to hold
|
|
@c the last printed file name and line number are accessed and modified
|
|
@c without synchronization; the update is not atomic and it occurs
|
|
@c before disabling cancellation, so it can be interrupted after only
|
|
@c one of the two variables is modified. After that, it's very much
|
|
@c like error.
|
|
|
|
The @code{error_at_line} function is very similar to the @code{error}
|
|
function. The only differences are the additional parameters @var{fname}
|
|
and @var{lineno}. The handling of the other parameters is identical to
|
|
that of @code{error} except that between the program name and the string
|
|
generated by the format string additional text is inserted.
|
|
|
|
Directly following the program name a colon, followed by the file name
|
|
pointed to by @var{fname}, another colon, and the value of @var{lineno} is
|
|
printed.
|
|
|
|
This additional output of course is meant to be used to locate an error
|
|
in an input file (like a programming language source code file etc).
|
|
|
|
If the global variable @code{error_one_per_line} is set to a non-zero
|
|
value @code{error_at_line} will avoid printing consecutive messages for
|
|
the same file and line. Repetition which are not directly following
|
|
each other are not caught.
|
|
|
|
Just like @code{error} this function only returns if @var{status} is
|
|
zero. Otherwise @code{exit} is called with the non-zero value. If
|
|
@code{error} returns, the global variable @code{error_message_count} is
|
|
incremented by one to keep track of the number of errors reported.
|
|
@end deftypefun
|
|
|
|
As mentioned above, the @code{error} and @code{error_at_line} functions
|
|
can be customized by defining a variable named
|
|
@code{error_print_progname}.
|
|
|
|
@deftypevar {void (*error_print_progname)} (void)
|
|
@standards{GNU, error.h}
|
|
If the @code{error_print_progname} variable is defined to a non-zero
|
|
value the function pointed to is called by @code{error} or
|
|
@code{error_at_line}. It is expected to print the program name or do
|
|
something similarly useful.
|
|
|
|
The function is expected to print to the @code{stderr} stream and
|
|
must be able to handle whatever orientation the stream has.
|
|
|
|
The variable is global and shared by all threads.
|
|
@end deftypevar
|
|
|
|
@deftypevar {unsigned int} error_message_count
|
|
@standards{GNU, error.h}
|
|
The @code{error_message_count} variable is incremented whenever one of
|
|
the functions @code{error} or @code{error_at_line} returns. The
|
|
variable is global and shared by all threads.
|
|
@end deftypevar
|
|
|
|
@deftypevar int error_one_per_line
|
|
@standards{GNU, error.h}
|
|
The @code{error_one_per_line} variable influences only
|
|
@code{error_at_line}. Normally the @code{error_at_line} function
|
|
creates output for every invocation. If @code{error_one_per_line} is
|
|
set to a non-zero value @code{error_at_line} keeps track of the last
|
|
file name and line number for which an error was reported and avoids
|
|
directly following messages for the same file and line. This variable
|
|
is global and shared by all threads.
|
|
@end deftypevar
|
|
|
|
@noindent
|
|
A program which read some input file and reports errors in it could look
|
|
like this:
|
|
|
|
@smallexample
|
|
@{
|
|
char *line = NULL;
|
|
size_t len = 0;
|
|
unsigned int lineno = 0;
|
|
|
|
error_message_count = 0;
|
|
while (! feof_unlocked (fp))
|
|
@{
|
|
ssize_t n = getline (&line, &len, fp);
|
|
if (n <= 0)
|
|
/* @r{End of file or error.} */
|
|
break;
|
|
++lineno;
|
|
|
|
/* @r{Process the line.} */
|
|
@dots{}
|
|
|
|
if (@r{Detect error in line})
|
|
error_at_line (0, errval, filename, lineno,
|
|
"some error text %s", some_variable);
|
|
@}
|
|
|
|
if (error_message_count != 0)
|
|
error (EXIT_FAILURE, 0, "%u errors found", error_message_count);
|
|
@}
|
|
@end smallexample
|
|
|
|
@code{error} and @code{error_at_line} are clearly the functions of
|
|
choice and enable the programmer to write applications which follow the
|
|
GNU coding standard. @Theglibc{} additionally contains functions which
|
|
are used in BSD for the same purpose. These functions are declared in
|
|
@file{err.h}. It is generally advised to not use these functions. They
|
|
are included only for compatibility.
|
|
|
|
@deftypefun void warn (const char *@var{format}, @dots{})
|
|
@standards{BSD, err.h}
|
|
@safety{@prelim{}@mtsafe{@mtslocale{}}@asunsafe{@asucorrupt{} @ascuheap{} @ascuintl{}}@acunsafe{@acucorrupt{} @aculock{} @acsmem{}}}
|
|
@c Just calls vwarn with the va_list.
|
|
The @code{warn} function is roughly equivalent to a call like
|
|
@smallexample
|
|
error (0, errno, format, @r{the parameters})
|
|
@end smallexample
|
|
@noindent
|
|
except that the global variables @code{error} respects and modifies
|
|
are not used.
|
|
@end deftypefun
|
|
|
|
@deftypefun void vwarn (const char *@var{format}, va_list @var{ap})
|
|
@standards{BSD, err.h}
|
|
@safety{@prelim{}@mtsafe{@mtslocale{}}@asunsafe{@asucorrupt{} @ascuheap{} @ascuintl{}}@acunsafe{@acucorrupt{} @aculock{} @acsmem{}}}
|
|
@c While holding stderr's recursive lock, it prints the programname, the
|
|
@c given message, and the error string with fw?printf's %m. When the
|
|
@c stream is wide, convert_and_print converts the format string to an
|
|
@c alloca/malloc-created buffer using mbsrtowcs and then calls fwprintf.
|
|
The @code{vwarn} function is just like @code{warn} except that the
|
|
parameters for the handling of the format string @var{format} are passed
|
|
in as a value of type @code{va_list}.
|
|
@end deftypefun
|
|
|
|
@deftypefun void warnx (const char *@var{format}, @dots{})
|
|
@standards{BSD, err.h}
|
|
@safety{@prelim{}@mtsafe{@mtslocale{}}@asunsafe{@asucorrupt{} @ascuheap{}}@acunsafe{@acucorrupt{} @aculock{} @acsmem{}}}
|
|
@c Same as warn, but without the strerror translation issues.
|
|
The @code{warnx} function is roughly equivalent to a call like
|
|
@smallexample
|
|
error (0, 0, format, @r{the parameters})
|
|
@end smallexample
|
|
@noindent
|
|
except that the global variables @code{error} respects and modifies
|
|
are not used. The difference to @code{warn} is that no error number
|
|
string is printed.
|
|
@end deftypefun
|
|
|
|
@deftypefun void vwarnx (const char *@var{format}, va_list @var{ap})
|
|
@standards{BSD, err.h}
|
|
@safety{@prelim{}@mtsafe{@mtslocale{}}@asunsafe{@asucorrupt{} @ascuheap{}}@acunsafe{@acucorrupt{} @aculock{} @acsmem{}}}
|
|
@c Same as vwarn, but without the strerror translation issues.
|
|
The @code{vwarnx} function is just like @code{warnx} except that the
|
|
parameters for the handling of the format string @var{format} are passed
|
|
in as a value of type @code{va_list}.
|
|
@end deftypefun
|
|
|
|
@deftypefun void err (int @var{status}, const char *@var{format}, @dots{})
|
|
@standards{BSD, err.h}
|
|
@safety{@prelim{}@mtsafe{@mtslocale{}}@asunsafe{@asucorrupt{} @ascuheap{} @ascuintl{}}@acunsafe{@acucorrupt{} @aculock{} @acsmem{}}}
|
|
@c Same as warn followed by exit.
|
|
The @code{err} function is roughly equivalent to a call like
|
|
@smallexample
|
|
error (status, errno, format, @r{the parameters})
|
|
@end smallexample
|
|
@noindent
|
|
except that the global variables @code{error} respects and modifies
|
|
are not used and that the program is exited even if @var{status} is zero.
|
|
@end deftypefun
|
|
|
|
@deftypefun void verr (int @var{status}, const char *@var{format}, va_list @var{ap})
|
|
@standards{BSD, err.h}
|
|
@safety{@prelim{}@mtsafe{@mtslocale{}}@asunsafe{@asucorrupt{} @ascuheap{} @ascuintl{}}@acunsafe{@acucorrupt{} @aculock{} @acsmem{}}}
|
|
@c Same as vwarn followed by exit.
|
|
The @code{verr} function is just like @code{err} except that the
|
|
parameters for the handling of the format string @var{format} are passed
|
|
in as a value of type @code{va_list}.
|
|
@end deftypefun
|
|
|
|
@deftypefun void errx (int @var{status}, const char *@var{format}, @dots{})
|
|
@standards{BSD, err.h}
|
|
@safety{@prelim{}@mtsafe{@mtslocale{}}@asunsafe{@asucorrupt{} @ascuheap{}}@acunsafe{@acucorrupt{} @aculock{} @acsmem{}}}
|
|
@c Same as warnx followed by exit.
|
|
The @code{errx} function is roughly equivalent to a call like
|
|
@smallexample
|
|
error (status, 0, format, @r{the parameters})
|
|
@end smallexample
|
|
@noindent
|
|
except that the global variables @code{error} respects and modifies
|
|
are not used and that the program is exited even if @var{status}
|
|
is zero. The difference to @code{err} is that no error number
|
|
string is printed.
|
|
@end deftypefun
|
|
|
|
@deftypefun void verrx (int @var{status}, const char *@var{format}, va_list @var{ap})
|
|
@standards{BSD, err.h}
|
|
@safety{@prelim{}@mtsafe{@mtslocale{}}@asunsafe{@asucorrupt{} @ascuheap{}}@acunsafe{@acucorrupt{} @aculock{} @acsmem{}}}
|
|
@c Same as vwarnx followed by exit.
|
|
The @code{verrx} function is just like @code{errx} except that the
|
|
parameters for the handling of the format string @var{format} are passed
|
|
in as a value of type @code{va_list}.
|
|
@end deftypefun
|