The Open(name) command opens a file for reading and writing of text data.

There are three optional arguments: create, overwrite, and append. Each accepts the values true or false.

create = true or false

The create optional argument determines the behavior when file does not exist.  If create is true, then file is created.  If create is false, an error is raised.  If file does exist, this argument has no effect.  By default, create is true.

overwrite = true or false

The overwrite optional argument determines the behavior when file does exist.  If overwrite is true, then the file is overwritten.  If overwrite is false, the contents of the previous file are visible.  If file does not exist, this argument has no effect.  By default, overwrite is false.

append = true or false

The append optional argument determines the initial file position after file has been opened. If append is true, then the initial file position is at the end of the file; otherwise, it is at the beginning of the file.  If file is created or overwrites a previous value, this argument has no effect.  By default, append is false.

In many cases, it is not necessary to Open a file in order to access it. The first operation performed on a file opens it. The Open function allows you to control the opening mode.

If the file being opened is already open, Open raises an error.

If the limit for the maximum number of simultaneously open files has been reached, Open raises an error.

For information on filenames, see file.

$\mathrm{fd}≔\mathrm{FileTools}\left[\mathrm{Text}\right]\left[\mathrm{Open}\right]\left(\mathrm{testfile}\,\mathrm{create}\,\mathrm{overwrite}\right)$

$\mathrm{fd}≔0$

$\mathrm{FileTools}\left[\mathrm{Text}\right]\left[\mathrm{WriteString}\right]\left(\mathrm{fd}\,''This\; is\; a\; test\backslash n''\right)$

$15$

$\mathrm{FileTools}\left[\mathrm{Text}\right]\left[\mathrm{Close}\right]\left(\mathrm{fd}\right)$