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| <h3 class="section">17.1 Identifying Terminals</h3> |
| |
| <p><a name="index-terminal-identification-1845"></a><a name="index-identifying-terminals-1846"></a> |
| The functions described in this chapter only work on files that |
| correspond to terminal devices. You can find out whether a file |
| descriptor is associated with a terminal by using the <code>isatty</code> |
| function. |
| |
| <p><a name="index-unistd_002eh-1847"></a>Prototypes for the functions in this section are declared in the header |
| file <samp><span class="file">unistd.h</span></samp>. |
| |
| <!-- unistd.h --> |
| <!-- POSIX.1 --> |
| <div class="defun"> |
| — Function: int <b>isatty</b> (<var>int filedes</var>)<var><a name="index-isatty-1848"></a></var><br> |
| <blockquote><p>This function returns <code>1</code> if <var>filedes</var> is a file descriptor |
| associated with an open terminal device, and 0 otherwise. |
| </p></blockquote></div> |
| |
| <p>If a file descriptor is associated with a terminal, you can get its |
| associated file name using the <code>ttyname</code> function. See also the |
| <code>ctermid</code> function, described in <a href="Identifying-the-Terminal.html#Identifying-the-Terminal">Identifying the Terminal</a>. |
| |
| <!-- unistd.h --> |
| <!-- POSIX.1 --> |
| <div class="defun"> |
| — Function: char * <b>ttyname</b> (<var>int filedes</var>)<var><a name="index-ttyname-1849"></a></var><br> |
| <blockquote><p>If the file descriptor <var>filedes</var> is associated with a terminal |
| device, the <code>ttyname</code> function returns a pointer to a |
| statically-allocated, null-terminated string containing the file name of |
| the terminal file. The value is a null pointer if the file descriptor |
| isn't associated with a terminal, or the file name cannot be determined. |
| </p></blockquote></div> |
| |
| <!-- unistd.h --> |
| <!-- POSIX.1 --> |
| <div class="defun"> |
| — Function: int <b>ttyname_r</b> (<var>int filedes, char *buf, size_t len</var>)<var><a name="index-ttyname_005fr-1850"></a></var><br> |
| <blockquote><p>The <code>ttyname_r</code> function is similar to the <code>ttyname</code> function |
| except that it places its result into the user-specified buffer starting |
| at <var>buf</var> with length <var>len</var>. |
| |
| <p>The normal return value from <code>ttyname_r</code> is 0. Otherwise an |
| error number is returned to indicate the 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>ENOTTY</code><dd>The <var>filedes</var> is not associated with a terminal. |
| |
| <br><dt><code>ERANGE</code><dd>The buffer length <var>len</var> is too small to store the string to be |
| returned. |
| </dl> |
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