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8.1 KiB
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136 lines
8.1 KiB
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<html lang="en">
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<head>
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<title>Environment - Debugging with GDB</title>
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<meta name="description" content="Debugging with GDB">
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<link title="Top" rel="start" href="index.html#Top">
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<link rel="up" href="Running.html#Running" title="Running">
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<link rel="prev" href="Arguments.html#Arguments" title="Arguments">
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<link rel="next" href="Working-Directory.html#Working-Directory" title="Working Directory">
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Copyright (C) 1988-2019 Free Software Foundation, Inc.
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Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.3 or
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any later version published by the Free Software Foundation; with the
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<body>
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<div class="node">
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<a name="Environment"></a>
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<p>
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Next: <a rel="next" accesskey="n" href="Working-Directory.html#Working-Directory">Working Directory</a>,
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Previous: <a rel="previous" accesskey="p" href="Arguments.html#Arguments">Arguments</a>,
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Up: <a rel="up" accesskey="u" href="Running.html#Running">Running</a>
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<hr>
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</div>
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<h3 class="section">4.4 Your Program's Environment</h3>
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<p><a name="index-environment-_0028of-your-program_0029-129"></a>The <dfn>environment</dfn> consists of a set of environment variables and
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their values. Environment variables conventionally record such things as
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your user name, your home directory, your terminal type, and your search
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path for programs to run. Usually you set up environment variables with
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the shell and they are inherited by all the other programs you run. When
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debugging, it can be useful to try running your program with a modified
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environment without having to start <span class="sc">gdb</span> over again.
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<a name="index-path-130"></a>
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<dl><dt><code>path </code><var>directory</var><dd>Add <var>directory</var> to the front of the <code>PATH</code> environment variable
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(the search path for executables) that will be passed to your program.
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The value of <code>PATH</code> used by <span class="sc">gdb</span> does not change.
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You may specify several directory names, separated by whitespace or by a
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system-dependent separator character (‘<samp><span class="samp">:</span></samp>’ on Unix, ‘<samp><span class="samp">;</span></samp>’ on
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MS-DOS and MS-Windows). If <var>directory</var> is already in the path, it
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is moved to the front, so it is searched sooner.
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<p>You can use the string ‘<samp><span class="samp">$cwd</span></samp>’ to refer to whatever is the current
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working directory at the time <span class="sc">gdb</span> searches the path. If you
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use ‘<samp><span class="samp">.</span></samp>’ instead, it refers to the directory where you executed the
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<code>path</code> command. <span class="sc">gdb</span> replaces ‘<samp><span class="samp">.</span></samp>’ in the
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<var>directory</var> argument (with the current path) before adding
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<var>directory</var> to the search path.
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<!-- 'path' is explicitly nonrepeatable, but RMS points out it is silly to -->
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<!-- document that, since repeating it would be a no-op. -->
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<p><a name="index-show-paths-131"></a><br><dt><code>show paths</code><dd>Display the list of search paths for executables (the <code>PATH</code>
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environment variable).
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<p><a name="index-show-environment-132"></a><br><dt><code>show environment </code><span class="roman">[</span><var>varname</var><span class="roman">]</span><dd>Print the value of environment variable <var>varname</var> to be given to
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your program when it starts. If you do not supply <var>varname</var>,
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print the names and values of all environment variables to be given to
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your program. You can abbreviate <code>environment</code> as <code>env</code>.
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<p><a name="index-set-environment-133"></a><a name="set-environment"></a><br><dt><code>set environment </code><var>varname</var> <span class="roman">[</span><code>=</code><var>value</var><span class="roman">]</span><dd>Set environment variable <var>varname</var> to <var>value</var>. The value
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changes for your program (and the shell <span class="sc">gdb</span> uses to launch
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it), not for <span class="sc">gdb</span> itself. The <var>value</var> may be any string; the
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values of environment variables are just strings, and any
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interpretation is supplied by your program itself. The <var>value</var>
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parameter is optional; if it is eliminated, the variable is set to a
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null value.
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<!-- "any string" here does not include leading, trailing -->
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<!-- blanks. Gnu asks: does anyone care? -->
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<p>For example, this command:
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<pre class="smallexample"> set env USER = foo
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</pre>
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<p class="noindent">tells the debugged program, when subsequently run, that its user is named
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‘<samp><span class="samp">foo</span></samp>’. (The spaces around ‘<samp><span class="samp">=</span></samp>’ are used for clarity here; they
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are not actually required.)
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<p>Note that on Unix systems, <span class="sc">gdb</span> runs your program via a shell,
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which also inherits the environment set with <code>set environment</code>.
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If necessary, you can avoid that by using the ‘<samp><span class="samp">env</span></samp>’ program as a
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wrapper instead of using <code>set environment</code>. See <a href="set-exec_002dwrapper.html#set-exec_002dwrapper">set exec-wrapper</a>, for an example doing just that.
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<p>Environment variables that are set by the user are also transmitted to
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<samp><span class="command">gdbserver</span></samp> to be used when starting the remote inferior.
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see <a href="QEnvironmentHexEncoded.html#QEnvironmentHexEncoded">QEnvironmentHexEncoded</a>.
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<p><a name="index-unset-environment-134"></a><a name="unset-environment"></a><br><dt><code>unset environment </code><var>varname</var><dd>Remove variable <var>varname</var> from the environment to be passed to your
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program. This is different from ‘<samp><span class="samp">set env </span><var>varname</var><span class="samp"> =</span></samp>’;
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<code>unset environment</code> removes the variable from the environment,
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rather than assigning it an empty value.
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<p>Environment variables that are unset by the user are also unset on
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<samp><span class="command">gdbserver</span></samp> when starting the remote inferior.
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see <a href="QEnvironmentUnset.html#QEnvironmentUnset">QEnvironmentUnset</a>.
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</dl>
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<p><em>Warning:</em> On Unix systems, <span class="sc">gdb</span> runs your program using
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the shell indicated by your <code>SHELL</code> environment variable if it
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exists (or <code>/bin/sh</code> if not). If your <code>SHELL</code> variable
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names a shell that runs an initialization file when started
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non-interactively—such as <samp><span class="file">.cshrc</span></samp> for C-shell, $<samp><span class="file">.zshenv</span></samp>
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for the Z shell, or the file specified in the ‘<samp><span class="samp">BASH_ENV</span></samp>’
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environment variable for BASH—any variables you set in that file
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affect your program. You may wish to move setting of environment
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variables to files that are only run when you sign on, such as
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<samp><span class="file">.login</span></samp> or <samp><span class="file">.profile</span></samp>.
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</body></html>
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