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| <h3 class="section">4.11 <code>fgetpos</code>—record position in a stream or file</h3> |
| |
| <p><a name="index-fgetpos-166"></a><a name="index-g_t_005ffgetpos_005fr-167"></a><strong>Synopsis</strong> |
| <pre class="example"> #include <stdio.h> |
| int fgetpos(FILE *<var>fp</var>, fpos_t *<var>pos</var>); |
| int _fgetpos_r(struct _reent *<var>ptr</var>, FILE *<var>fp</var>, fpos_t *<var>pos</var>); |
| |
| </pre> |
| <p><strong>Description</strong><br> |
| Objects of type <code>FILE</code> can have a “position” that records how much |
| of the file your program has already read. Many of the <code>stdio</code> functions |
| depend on this position, and many change it as a side effect. |
| |
| <p>You can use <code>fgetpos</code> to report on the current position for a file |
| identified by <var>fp</var>; <code>fgetpos</code> will write a value |
| representing that position at <code>*</code><var>pos</var>. Later, you can |
| use this value with <code>fsetpos</code> to return the file to this |
| position. |
| |
| <p>In the current implementation, <code>fgetpos</code> simply uses a character |
| count to represent the file position; this is the same number that |
| would be returned by <code>ftell</code>. |
| |
| <p><br> |
| <strong>Returns</strong><br> |
| <code>fgetpos</code> returns <code>0</code> when successful. If <code>fgetpos</code> fails, the |
| result is <code>1</code>. Failure occurs on streams that do not support |
| positioning; the global <code>errno</code> indicates this condition with the |
| value <code>ESPIPE</code>. |
| |
| <p><br> |
| <strong>Portability</strong><br> |
| <code>fgetpos</code> is required by the ANSI C standard, but the meaning of the |
| value it records is not specified beyond requiring that it be |
| acceptable as an argument to <code>fsetpos</code>. In particular, other |
| conforming C implementations may return a different result from |
| <code>ftell</code> than what <code>fgetpos</code> writes at <code>*</code><var>pos</var>. |
| |
| <p>No supporting OS subroutines are required. |
| |
| <p><br> |
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