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| <h4 class="subsection">27.7.2 Process Group Functions</h4> |
| |
| <p>Here are descriptions of the functions for manipulating process groups. |
| Your program should include the header files <samp><span class="file">sys/types.h</span></samp> and |
| <samp><span class="file">unistd.h</span></samp> to use these functions. |
| <a name="index-unistd_002eh-3232"></a><a name="index-sys_002ftypes_002eh-3233"></a> |
| <!-- unistd.h --> |
| <!-- POSIX.1 --> |
| |
| <div class="defun"> |
| — Function: pid_t <b>setsid</b> (<var>void</var>)<var><a name="index-setsid-3234"></a></var><br> |
| <blockquote><p>The <code>setsid</code> function creates a new session. The calling process |
| becomes the session leader, and is put in a new process group whose |
| process group ID is the same as the process ID of that process. There |
| are initially no other processes in the new process group, and no other |
| process groups in the new session. |
| |
| <p>This function also makes the calling process have no controlling terminal. |
| |
| <p>The <code>setsid</code> function returns the new process group ID of the |
| calling process if successful. A return value of <code>-1</code> indicates an |
| error. The following <code>errno</code> error conditions are defined for this |
| function: |
| |
| <dl> |
| <dt><code>EPERM</code><dd>The calling process is already a process group leader, or there is |
| already another process group around that has the same process group ID. |
| </dl> |
| </p></blockquote></div> |
| |
| <!-- unistd.h --> |
| <!-- SVID --> |
| <div class="defun"> |
| — Function: pid_t <b>getsid</b> (<var>pid_t pid</var>)<var><a name="index-getsid-3235"></a></var><br> |
| <blockquote> |
| <p>The <code>getsid</code> function returns the process group ID of the session |
| leader of the specified process. If a <var>pid</var> is <code>0</code>, the |
| process group ID of the session leader of the current process is |
| returned. |
| |
| <p>In case of error <code>-1</code> is returned and <code>errno</code> is set. The |
| following <code>errno</code> error conditions are defined for this function: |
| |
| <dl> |
| <dt><code>ESRCH</code><dd>There is no process with the given process ID <var>pid</var>. |
| <br><dt><code>EPERM</code><dd>The calling process and the process specified by <var>pid</var> are in |
| different sessions, and the implementation doesn't allow to access the |
| process group ID of the session leader of the process with ID <var>pid</var> |
| from the calling process. |
| </dl> |
| </p></blockquote></div> |
| |
| <p>The <code>getpgrp</code> function has two definitions: one derived from BSD |
| Unix, and one from the POSIX.1 standard. The feature test macros you |
| have selected (see <a href="Feature-Test-Macros.html#Feature-Test-Macros">Feature Test Macros</a>) determine which definition |
| you get. Specifically, you get the BSD version if you define |
| <code>_BSD_SOURCE</code>; otherwise, you get the POSIX version if you define |
| <code>_POSIX_SOURCE</code> or <code>_GNU_SOURCE</code>. Programs written for old |
| BSD systems will not include <samp><span class="file">unistd.h</span></samp>, which defines |
| <code>getpgrp</code> specially under <code>_BSD_SOURCE</code>. You must link such |
| programs with the <code>-lbsd-compat</code> option to get the BSD definition. |
| <a name="index-g_t_002dlbsd_002dcompat-3236"></a><a name="index-bsd_002dcompat-3237"></a><a name="index-BSD-compatibility-library-3238"></a> |
| <!-- unistd.h --> |
| <!-- POSIX.1 --> |
| |
| <div class="defun"> |
| — POSIX.1 Function: pid_t <b>getpgrp</b> (<var>void</var>)<var><a name="index-getpgrp-3239"></a></var><br> |
| <blockquote><p>The POSIX.1 definition of <code>getpgrp</code> returns the process group ID of |
| the calling process. |
| </p></blockquote></div> |
| |
| <!-- unistd.h --> |
| <!-- BSD --> |
| <div class="defun"> |
| — BSD Function: pid_t <b>getpgrp</b> (<var>pid_t pid</var>)<var><a name="index-getpgrp-3240"></a></var><br> |
| <blockquote><p>The BSD definition of <code>getpgrp</code> returns the process group ID of the |
| process <var>pid</var>. You can supply a value of <code>0</code> for the <var>pid</var> |
| argument to get information about the calling process. |
| </p></blockquote></div> |
| |
| <!-- unistd.h --> |
| <!-- SVID --> |
| <div class="defun"> |
| — System V Function: int <b>getpgid</b> (<var>pid_t pid</var>)<var><a name="index-getpgid-3241"></a></var><br> |
| <blockquote> |
| <p><code>getpgid</code> is the same as the BSD function <code>getpgrp</code>. It |
| returns the process group ID of the process <var>pid</var>. You can supply a |
| value of <code>0</code> for the <var>pid</var> argument to get information about |
| the calling process. |
| |
| <p>In case of error <code>-1</code> is returned and <code>errno</code> is set. The |
| following <code>errno</code> error conditions are defined for this function: |
| |
| <dl> |
| <dt><code>ESRCH</code><dd>There is no process with the given process ID <var>pid</var>. |
| The calling process and the process specified by <var>pid</var> are in |
| different sessions, and the implementation doesn't allow to access the |
| process group ID of the process with ID <var>pid</var> from the calling |
| process. |
| </dl> |
| </p></blockquote></div> |
| |
| <!-- unistd.h --> |
| <!-- POSIX.1 --> |
| <div class="defun"> |
| — Function: int <b>setpgid</b> (<var>pid_t pid, pid_t pgid</var>)<var><a name="index-setpgid-3242"></a></var><br> |
| <blockquote><p>The <code>setpgid</code> function puts the process <var>pid</var> into the process |
| group <var>pgid</var>. As a special case, either <var>pid</var> or <var>pgid</var> can |
| be zero to indicate the process ID of the calling process. |
| |
| <p>This function fails on a system that does not support job control. |
| See <a href="Job-Control-is-Optional.html#Job-Control-is-Optional">Job Control is Optional</a>, for more information. |
| |
| <p>If the operation is successful, <code>setpgid</code> returns zero. Otherwise |
| it returns <code>-1</code>. The following <code>errno</code> error conditions are |
| defined for this function: |
| |
| <dl> |
| <dt><code>EACCES</code><dd>The child process named by <var>pid</var> has executed an <code>exec</code> |
| function since it was forked. |
| |
| <br><dt><code>EINVAL</code><dd>The value of the <var>pgid</var> is not valid. |
| |
| <br><dt><code>ENOSYS</code><dd>The system doesn't support job control. |
| |
| <br><dt><code>EPERM</code><dd>The process indicated by the <var>pid</var> argument is a session leader, |
| or is not in the same session as the calling process, or the value of |
| the <var>pgid</var> argument doesn't match a process group ID in the same |
| session as the calling process. |
| |
| <br><dt><code>ESRCH</code><dd>The process indicated by the <var>pid</var> argument is not the calling |
| process or a child of the calling process. |
| </dl> |
| </p></blockquote></div> |
| |
| <!-- unistd.h --> |
| <!-- BSD --> |
| <div class="defun"> |
| — Function: int <b>setpgrp</b> (<var>pid_t pid, pid_t pgid</var>)<var><a name="index-setpgrp-3243"></a></var><br> |
| <blockquote><p>This is the BSD Unix name for <code>setpgid</code>. Both functions do exactly |
| the same thing. |
| </p></blockquote></div> |
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