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| <h4 class="subsection">17.8.2 Opening a Pseudo-Terminal Pair</h4> |
| |
| <p><a name="index-opening-a-pseudo_002dterminal-pair-2031"></a> |
| These functions, derived from BSD, are available in the separate |
| <samp><span class="file">libutil</span></samp> library, and declared in <samp><span class="file">pty.h</span></samp>. |
| |
| <!-- pty.h --> |
| <!-- BSD --> |
| <div class="defun"> |
| — Function: int <b>openpty</b> (<var>int *amaster, int *aslave, char *name, const struct termios *termp, const struct winsize *winp</var>)<var><a name="index-openpty-2032"></a></var><br> |
| <blockquote><p>This function allocates and opens a pseudo-terminal pair, returning the |
| file descriptor for the master in <var>*amaster</var>, and the file |
| descriptor for the slave in <var>*aslave</var>. If the argument <var>name</var> |
| is not a null pointer, the file name of the slave pseudo-terminal |
| device is stored in <code>*name</code>. If <var>termp</var> is not a null pointer, |
| the terminal attributes of the slave are set to the ones specified in |
| the structure that <var>termp</var> points to (see <a href="Terminal-Modes.html#Terminal-Modes">Terminal Modes</a>). |
| Likewise, if the <var>winp</var> is not a null pointer, the screen size of |
| the slave is set to the values specified in the structure that |
| <var>winp</var> points to. |
| |
| <p>The normal return value from <code>openpty</code> is 0; a value of |
| -1 is returned in case of failure. The following <code>errno</code> |
| conditions are defined for this function: |
| |
| <dl> |
| <dt><code>ENOENT</code><dd>There are no free pseudo-terminal pairs available. |
| </dl> |
| |
| <p><strong>Warning:</strong> Using the <code>openpty</code> function with <var>name</var> not |
| set to <code>NULL</code> is <strong>very dangerous</strong> because it provides no |
| protection against overflowing the string <var>name</var>. You should use |
| the <code>ttyname</code> function on the file descriptor returned in |
| <var>*slave</var> to find out the file name of the slave pseudo-terminal |
| device instead. |
| </p></blockquote></div> |
| |
| <!-- pty.h --> |
| <!-- BSD --> |
| <div class="defun"> |
| — Function: int <b>forkpty</b> (<var>int *amaster, char *name, const struct termios *termp, const struct winsize *winp</var>)<var><a name="index-forkpty-2033"></a></var><br> |
| <blockquote><p>This function is similar to the <code>openpty</code> function, but in |
| addition, forks a new process (see <a href="Creating-a-Process.html#Creating-a-Process">Creating a Process</a>) and makes the |
| newly opened slave pseudo-terminal device the controlling terminal |
| (see <a href="Controlling-Terminal.html#Controlling-Terminal">Controlling Terminal</a>) for the child process. |
| |
| <p>If the operation is successful, there are then both parent and child |
| processes and both see <code>forkpty</code> return, but with different values: |
| it returns a value of 0 in the child process and returns the child's |
| process ID in the parent process. |
| |
| <p>If the allocation of a pseudo-terminal pair or the process creation |
| failed, <code>forkpty</code> returns a value of -1 in the parent |
| process. |
| |
| <p><strong>Warning:</strong> The <code>forkpty</code> function has the same problems with |
| respect to the <var>name</var> argument as <code>openpty</code>. |
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