175 lines
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175 lines
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<title>The GNU Fortran Compiler: FSEEK</title>
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<body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000">
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<a name="FSEEK"></a>
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<div class="header">
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<p>
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Next: <a href="FSTAT.html#FSTAT" accesskey="n" rel="next">FSTAT</a>, Previous: <a href="FREE.html#FREE" accesskey="p" rel="prev">FREE</a>, Up: <a href="Intrinsic-Procedures.html#Intrinsic-Procedures" accesskey="u" rel="up">Intrinsic Procedures</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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<hr>
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<a name="FSEEK-_002d_002d_002d-Low-level-file-positioning-subroutine"></a>
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<h3 class="section">9.108 <code>FSEEK</code> — Low level file positioning subroutine</h3>
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<a name="index-FSEEK"></a>
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<a name="index-file-operation_002c-seek"></a>
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<a name="index-file-operation_002c-position"></a>
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<dl compact="compact">
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<dt><em>Description</em>:</dt>
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<dd><p>Moves <var>UNIT</var> to the specified <var>OFFSET</var>. If <var>WHENCE</var>
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is set to 0, the <var>OFFSET</var> is taken as an absolute value <code>SEEK_SET</code>,
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if set to 1, <var>OFFSET</var> is taken to be relative to the current position
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<code>SEEK_CUR</code>, and if set to 2 relative to the end of the file <code>SEEK_END</code>.
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On error, <var>STATUS</var> is set to a nonzero value. If <var>STATUS</var> the seek
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fails silently.
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</p>
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<p>This intrinsic routine is not fully backwards compatible with <code>g77</code>.
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In <code>g77</code>, the <code>FSEEK</code> takes a statement label instead of a
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<var>STATUS</var> variable. If FSEEK is used in old code, change
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</p><div class="smallexample">
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<pre class="smallexample"> CALL FSEEK(UNIT, OFFSET, WHENCE, *label)
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</pre></div>
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<p>to
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</p><div class="smallexample">
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<pre class="smallexample"> INTEGER :: status
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CALL FSEEK(UNIT, OFFSET, WHENCE, status)
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IF (status /= 0) GOTO label
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</pre></div>
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<p>Please note that GNU Fortran provides the Fortran 2003 Stream facility.
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Programmers should consider the use of new stream IO feature in new code
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for future portability. See also <a href="Fortran-2003-status.html#Fortran-2003-status">Fortran 2003 status</a>.
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</p>
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</dd>
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<dt><em>Standard</em>:</dt>
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<dd><p>GNU extension
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</p>
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</dd>
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<dt><em>Class</em>:</dt>
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<dd><p>Subroutine
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</p>
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</dd>
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<dt><em>Syntax</em>:</dt>
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<dd><p><code>CALL FSEEK(UNIT, OFFSET, WHENCE[, STATUS])</code>
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</p>
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</dd>
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<dt><em>Arguments</em>:</dt>
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<dd><table>
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<tr><td width="15%"><var>UNIT</var></td><td width="70%">Shall be a scalar of type <code>INTEGER</code>.</td></tr>
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<tr><td width="15%"><var>OFFSET</var></td><td width="70%">Shall be a scalar of type <code>INTEGER</code>.</td></tr>
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<tr><td width="15%"><var>WHENCE</var></td><td width="70%">Shall be a scalar of type <code>INTEGER</code>.
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Its value shall be either 0, 1 or 2.</td></tr>
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<tr><td width="15%"><var>STATUS</var></td><td width="70%">(Optional) shall be a scalar of type
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<code>INTEGER(4)</code>.</td></tr>
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</table>
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</dd>
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<dt><em>Example</em>:</dt>
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<dd><div class="smallexample">
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<pre class="smallexample">PROGRAM test_fseek
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INTEGER, PARAMETER :: SEEK_SET = 0, SEEK_CUR = 1, SEEK_END = 2
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INTEGER :: fd, offset, ierr
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ierr = 0
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offset = 5
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fd = 10
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OPEN(UNIT=fd, FILE="fseek.test")
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CALL FSEEK(fd, offset, SEEK_SET, ierr) ! move to OFFSET
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print *, FTELL(fd), ierr
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CALL FSEEK(fd, 0, SEEK_END, ierr) ! move to end
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print *, FTELL(fd), ierr
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CALL FSEEK(fd, 0, SEEK_SET, ierr) ! move to beginning
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print *, FTELL(fd), ierr
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CLOSE(UNIT=fd)
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END PROGRAM
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</pre></div>
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</dd>
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<dt><em>See also</em>:</dt>
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<dd><p><a href="FTELL.html#FTELL">FTELL</a>
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</p></dd>
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</dl>
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<hr>
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<div class="header">
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<p>
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Next: <a href="FSTAT.html#FSTAT" accesskey="n" rel="next">FSTAT</a>, Previous: <a href="FREE.html#FREE" accesskey="p" rel="prev">FREE</a>, Up: <a href="Intrinsic-Procedures.html#Intrinsic-Procedures" accesskey="u" rel="up">Intrinsic Procedures</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
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