The Position(file) command returns the current position within the specified file. This is the position to which the next write takes place, or from which the next read takes place.

The Position(file, pos) command sets the current position within the specified file and returns that new position.

A specified position of infinity sets the current position to the end of the file.

If file does not refer to an open file, an error is raised.

To determine a position suitable for passing to Position in a text file, call Position. Only values returned by Position(file) are guaranteed to be meaningful when used in Position(file, pos). Counting characters while reading and/or writing is not reliable, because newline characters are translated from/to local conventions, which may use more than a single character. However, Position(file, infinity) is always valid.

$\mathrm{testfile}≔\mathrm{FileTools}\left[\mathrm{TemporaryFile}\right]\left(''test''\right)$

$\mathrm{testfile}≔''/tmp/test''$

$\mathrm{FileTools}\left[\mathrm{Text}\right]\left[\mathrm{WriteFile}\right]\left(\mathrm{testfile}\,''This\; is\; a\; test.''\right)$

$15$

$\mathrm{FileTools}\left[\mathrm{Text}\right]\left[\mathrm{Open}\right]\left(\mathrm{testfile}\right)$

$\mathrm{FileTools}\left[\mathrm{Position}\right]\left(\mathrm{testfile}\,\mathrm{\infty }\right)$

$15$