Ensures that any output which has been written to the specified file, which is assumed to have been opened either implicitly or by fopen or popen, is actually written to disk.

fflush does not return anything.

When a file is closed, it is automatically flushed.

$\mathrm{fd}≔\mathrm{fopen}\left(\mathrm{testFile}\,\mathrm{WRITE}\,\mathrm{TEXT}\right)$

$\mathrm{fd}≔0$

$\mathrm{fprintf}\left(\mathrm{fd}\,\mathrm{`This\; is\; a\; test\; `}\right)$

$15$

$\mathrm{ssystem}\left(''cat\; testFile''\right)$

$\left[0\,''''\right]$

$\mathrm{fflush}\left(\mathrm{fd}\right)$

$\mathrm{ssystem}\left(''cat\; testFile''\right)$

$\left[0\,''This\; is\; a\; test''\right]$

$\mathrm{fclose}\left(\mathrm{fd}\right)$