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| <h3 class="section">4.38 <code>gets</code>—get character string (obsolete, use <code>fgets</code> instead)</h3> |
| |
| <p><a name="index-gets-225"></a><a name="index-g_t_005fgets_005fr-226"></a><strong>Synopsis</strong> |
| <pre class="example"> #include <stdio.h> |
| |
| char *gets(char *<var>buf</var>); |
| |
| char *_gets_r(struct _reent *<var>reent</var>, char *<var>buf</var>); |
| |
| </pre> |
| <p><strong>Description</strong><br> |
| Reads characters from standard input until a newline is found. |
| The characters up to the newline are stored in <var>buf</var>. The |
| newline is discarded, and the buffer is terminated with a 0. |
| |
| <p>This is a <em>dangerous</em> function, as it has no way of checking |
| the amount of space available in <var>buf</var>. One of the attacks |
| used by the Internet Worm of 1988 used this to overrun a |
| buffer allocated on the stack of the finger daemon and |
| overwrite the return address, causing the daemon to execute |
| code downloaded into it over the connection. |
| |
| <p>The alternate function <code>_gets_r</code> is a reentrant version. The extra |
| argument <var>reent</var> is a pointer to a reentrancy structure. |
| |
| <p><br> |
| <strong>Returns</strong><br> |
| <code>gets</code> returns the buffer passed to it, with the data filled |
| in. If end of file occurs with some data already accumulated, |
| the data is returned with no other indication. If end of file |
| occurs with no data in the buffer, NULL is returned. |
| |
| <p>Supporting OS subroutines required: <code>close</code>, <code>fstat</code>, <code>isatty</code>, |
| <code>lseek</code>, <code>read</code>, <code>sbrk</code>, <code>write</code>. |
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