Next: , Up: Invoking GDB

2.1.1 Choosing Files

When gdb starts, it reads any arguments other than options as specifying an executable file and core file (or process ID). This is the same as if the arguments were specified by the ‘-se’ and ‘-c’ (or ‘-p’) options respectively. (gdb reads the first argument that does not have an associated option flag as equivalent to the ‘-se’ option followed by that argument; and the second argument that does not have an associated option flag, if any, as equivalent to the ‘-c’/‘-p’ option followed by that argument.) If the second argument begins with a decimal digit, gdb will first attempt to attach to it as a process, and if that fails, attempt to open it as a corefile. If you have a corefile whose name begins with a digit, you can prevent gdb from treating it as a pid by prefixing it with ./, e.g. ./12345.

If gdb has not been configured to included core file support, such as for most embedded targets, then it will complain about a second argument and ignore it.

Many options have both long and short forms; both are shown in the following list. gdb also recognizes the long forms if you truncate them, so long as enough of the option is present to be unambiguous. (If you prefer, you can flag option arguments with ‘--’ rather than ‘-’, though we illustrate the more usual convention.)

-symbols file
-s file
Read symbol table from file file.
-exec file
-e file
Use file file as the executable file to execute when appropriate, and for examining pure data in conjunction with a core dump.
-se file
Read symbol table from file file and use it as the executable file.
-core file
-c file
Use file file as a core dump to examine.
-pid number
-p number
Connect to process ID number, as with the attach command.
-command file
-x file
Execute commands from file file. The contents of this file is evaluated exactly as the source command would. See Command files.
-eval-command command
-ex command
Execute a single gdb command.

This option may be used multiple times to call multiple commands. It may also be interleaved with ‘-command’ as required. 

          gdb -ex 'target sim' -ex 'load' \
             -x setbreakpoints -ex 'run' a.out

-init-command file
-ix file
Execute commands from file file before loading the inferior (but after loading gdbinit files). See Startup.
-init-eval-command command
-iex command
Execute a single gdb command before loading the inferior (but after loading gdbinit files). See Startup.
-directory directory
-d directory
Add directory to the path to search for source and script files.
-r
-readnow
Read each symbol file's entire symbol table immediately, rather than the default, which is to read it incrementally as it is needed. This makes startup slower, but makes future operations faster.
--readnever
Do not read each symbol file's symbolic debug information. This makes startup faster but at the expense of not being able to perform symbolic debugging. DWARF unwind information is also not read, meaning backtraces may become incomplete or inaccurate. One use of this is when a user simply wants to do the following sequence: attach, dump core, detach. Loading the debugging information in this case is an unnecessary cause of delay.