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| <title>The GNU Fortran Compiler: FSEEK</title> |
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| <a name="FSEEK-_002d_002d_002d-Low-level-file-positioning-subroutine"></a> |
| <h3 class="section">8.93 <code>FSEEK</code> — Low level file positioning subroutine</h3> |
| <a name="index-FSEEK"></a> |
| <a name="index-file-operation_002c-seek"></a> |
| <a name="index-file-operation_002c-position"></a> |
| |
| <dl compact="compact"> |
| <dt><em>Description</em>:</dt> |
| <dd><p>Moves <var>UNIT</var> to the specified <var>OFFSET</var>. If <var>WHENCE</var> |
| is set to 0, the <var>OFFSET</var> is taken as an absolute value <code>SEEK_SET</code>, |
| if set to 1, <var>OFFSET</var> is taken to be relative to the current position |
| <code>SEEK_CUR</code>, and if set to 2 relative to the end of the file <code>SEEK_END</code>. |
| On error, <var>STATUS</var> is set to a nonzero value. If <var>STATUS</var> the seek |
| fails silently. |
| </p> |
| <p>This intrinsic routine is not fully backwards compatible with <code>g77</code>. |
| In <code>g77</code>, the <code>FSEEK</code> takes a statement label instead of a |
| <var>STATUS</var> variable. If FSEEK is used in old code, change |
| </p><div class="smallexample"> |
| <pre class="smallexample"> CALL FSEEK(UNIT, OFFSET, WHENCE, *label) |
| </pre></div> |
| <p>to |
| </p><div class="smallexample"> |
| <pre class="smallexample"> INTEGER :: status |
| CALL FSEEK(UNIT, OFFSET, WHENCE, status) |
| IF (status /= 0) GOTO label |
| </pre></div> |
| |
| <p>Please note that GNU Fortran provides the Fortran 2003 Stream facility. |
| Programmers should consider the use of new stream IO feature in new code |
| for future portability. See also <a href="Fortran-2003-status.html#Fortran-2003-status">Fortran 2003 status</a>. |
| </p> |
| </dd> |
| <dt><em>Standard</em>:</dt> |
| <dd><p>GNU extension |
| </p> |
| </dd> |
| <dt><em>Class</em>:</dt> |
| <dd><p>Subroutine |
| </p> |
| </dd> |
| <dt><em>Syntax</em>:</dt> |
| <dd><p><code>CALL FSEEK(UNIT, OFFSET, WHENCE[, STATUS])</code> |
| </p> |
| </dd> |
| <dt><em>Arguments</em>:</dt> |
| <dd><table> |
| <tr><td width="15%"><var>UNIT</var></td><td width="70%">Shall be a scalar of type <code>INTEGER</code>.</td></tr> |
| <tr><td width="15%"><var>OFFSET</var></td><td width="70%">Shall be a scalar of type <code>INTEGER</code>.</td></tr> |
| <tr><td width="15%"><var>WHENCE</var></td><td width="70%">Shall be a scalar of type <code>INTEGER</code>. |
| Its value shall be either 0, 1 or 2.</td></tr> |
| <tr><td width="15%"><var>STATUS</var></td><td width="70%">(Optional) shall be a scalar of type |
| <code>INTEGER(4)</code>.</td></tr> |
| </table> |
| |
| </dd> |
| <dt><em>Example</em>:</dt> |
| <dd><div class="smallexample"> |
| <pre class="smallexample">PROGRAM test_fseek |
| INTEGER, PARAMETER :: SEEK_SET = 0, SEEK_CUR = 1, SEEK_END = 2 |
| INTEGER :: fd, offset, ierr |
| |
| ierr = 0 |
| offset = 5 |
| fd = 10 |
| |
| OPEN(UNIT=fd, FILE="fseek.test") |
| CALL FSEEK(fd, offset, SEEK_SET, ierr) ! move to OFFSET |
| print *, FTELL(fd), ierr |
| |
| CALL FSEEK(fd, 0, SEEK_END, ierr) ! move to end |
| print *, FTELL(fd), ierr |
| |
| CALL FSEEK(fd, 0, SEEK_SET, ierr) ! move to beginning |
| print *, FTELL(fd), ierr |
| |
| CLOSE(UNIT=fd) |
| END PROGRAM |
| </pre></div> |
| |
| </dd> |
| <dt><em>See also</em>:</dt> |
| <dd><p><a href="FTELL.html#FTELL">FTELL</a> |
| </p></dd> |
| </dl> |
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