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| <title>The GNU Fortran Compiler: FLUSH</title> |
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| <a name="FLUSH-_002d_002d_002d-Flush-I_002fO-unit_0028s_0029"></a> |
| <h3 class="section">8.87 <code>FLUSH</code> — Flush I/O unit(s)</h3> |
| <a name="index-FLUSH"></a> |
| <a name="index-file-operation_002c-flush"></a> |
| |
| <dl compact="compact"> |
| <dt><em>Description</em>:</dt> |
| <dd><p>Flushes Fortran unit(s) currently open for output. Without the optional |
| argument, all units are flushed, otherwise just the unit specified. |
| </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 FLUSH(UNIT)</code> |
| </p> |
| </dd> |
| <dt><em>Arguments</em>:</dt> |
| <dd><table> |
| <tr><td width="15%"><var>UNIT</var></td><td width="70%">(Optional) The type shall be <code>INTEGER</code>.</td></tr> |
| </table> |
| |
| </dd> |
| <dt><em>Note</em>:</dt> |
| <dd><p>Beginning with the Fortran 2003 standard, there is a <code>FLUSH</code> |
| statement that should be preferred over the <code>FLUSH</code> intrinsic. |
| </p> |
| <p>The <code>FLUSH</code> intrinsic and the Fortran 2003 <code>FLUSH</code> statement |
| have identical effect: they flush the runtime library’s I/O buffer so |
| that the data becomes visible to other processes. This does not guarantee |
| that the data is committed to disk. |
| </p> |
| <p>On POSIX systems, you can request that all data is transferred to the |
| storage device by calling the <code>fsync</code> function, with the POSIX file |
| descriptor of the I/O unit as argument (retrieved with GNU intrinsic |
| <code>FNUM</code>). The following example shows how: |
| </p> |
| <div class="smallexample"> |
| <pre class="smallexample"> ! Declare the interface for POSIX fsync function |
| interface |
| function fsync (fd) bind(c,name="fsync") |
| use iso_c_binding, only: c_int |
| integer(c_int), value :: fd |
| integer(c_int) :: fsync |
| end function fsync |
| end interface |
| |
| ! Variable declaration |
| integer :: ret |
| |
| ! Opening unit 10 |
| open (10,file="foo") |
| |
| ! ... |
| ! Perform I/O on unit 10 |
| ! ... |
| |
| ! Flush and sync |
| flush(10) |
| ret = fsync(fnum(10)) |
| |
| ! Handle possible error |
| if (ret /= 0) stop "Error calling FSYNC" |
| </pre></div> |
| |
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