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| <h4 class="subsection">27.7.3 Functions for Controlling Terminal Access</h4> |
| |
| <p>These are the functions for reading or setting the foreground |
| process group of a terminal. You should include the header files |
| <samp><span class="file">sys/types.h</span></samp> and <samp><span class="file">unistd.h</span></samp> in your application to use |
| these functions. |
| <a name="index-unistd_002eh-3244"></a><a name="index-sys_002ftypes_002eh-3245"></a> |
| Although these functions take a file descriptor argument to specify |
| the terminal device, the foreground job is associated with the terminal |
| file itself and not a particular open file descriptor. |
| |
| <!-- unistd.h --> |
| <!-- POSIX.1 --> |
| <div class="defun"> |
| — Function: pid_t <b>tcgetpgrp</b> (<var>int filedes</var>)<var><a name="index-tcgetpgrp-3246"></a></var><br> |
| <blockquote><p>This function returns the process group ID of the foreground process |
| group associated with the terminal open on descriptor <var>filedes</var>. |
| |
| <p>If there is no foreground process group, the return value is a number |
| greater than <code>1</code> that does not match the process group ID of any |
| existing process group. This can happen if all of the processes in the |
| job that was formerly the foreground job have terminated, and no other |
| job has yet been moved into the foreground. |
| |
| <p>In case of an error, a value of <code>-1</code> is returned. The |
| following <code>errno</code> error conditions are defined for this function: |
| |
| <dl> |
| <dt><code>EBADF</code><dd>The <var>filedes</var> argument is not a valid file descriptor. |
| |
| <br><dt><code>ENOSYS</code><dd>The system doesn't support job control. |
| |
| <br><dt><code>ENOTTY</code><dd>The terminal file associated with the <var>filedes</var> argument isn't the |
| controlling terminal of the calling process. |
| </dl> |
| </p></blockquote></div> |
| |
| <!-- unistd.h --> |
| <!-- POSIX.1 --> |
| <div class="defun"> |
| — Function: int <b>tcsetpgrp</b> (<var>int filedes, pid_t pgid</var>)<var><a name="index-tcsetpgrp-3247"></a></var><br> |
| <blockquote><p>This function is used to set a terminal's foreground process group ID. |
| The argument <var>filedes</var> is a descriptor which specifies the terminal; |
| <var>pgid</var> specifies the process group. The calling process must be a |
| member of the same session as <var>pgid</var> and must have the same |
| controlling terminal. |
| |
| <p>For terminal access purposes, this function is treated as output. If it |
| is called from a background process on its controlling terminal, |
| normally all processes in the process group are sent a <code>SIGTTOU</code> |
| signal. The exception is if the calling process itself is ignoring or |
| blocking <code>SIGTTOU</code> signals, in which case the operation is |
| performed and no signal is sent. |
| |
| <p>If successful, <code>tcsetpgrp</code> returns <code>0</code>. 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>EBADF</code><dd>The <var>filedes</var> argument is not a valid file descriptor. |
| |
| <br><dt><code>EINVAL</code><dd>The <var>pgid</var> argument is not valid. |
| |
| <br><dt><code>ENOSYS</code><dd>The system doesn't support job control. |
| |
| <br><dt><code>ENOTTY</code><dd>The <var>filedes</var> isn't the controlling terminal of the calling process. |
| |
| <br><dt><code>EPERM</code><dd>The <var>pgid</var> isn't a process group in the same session as the calling |
| process. |
| </dl> |
| </p></blockquote></div> |
| |
| <!-- termios.h --> |
| <!-- Unix98 --> |
| <div class="defun"> |
| — Function: pid_t <b>tcgetsid</b> (<var>int fildes</var>)<var><a name="index-tcgetsid-3248"></a></var><br> |
| <blockquote><p>This function is used to obtain the process group ID of the session |
| for which the terminal specified by <var>fildes</var> is the controlling terminal. |
| If the call is successful the group ID is returned. Otherwise the |
| return value is <code>(pid_t) -1</code> and the global variable <var>errno</var> |
| is set to the following value: |
| <dl> |
| <dt><code>EBADF</code><dd>The <var>filedes</var> argument is not a valid file descriptor. |
| |
| <br><dt><code>ENOTTY</code><dd>The calling process does not have a controlling terminal, or the file |
| is not the controlling terminal. |
| </dl> |
| </p></blockquote></div> |
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