The call type(e, 'filename') checks whether the expression e may be a valid file name.  An expression is defined to be of type filename if it is either a string or one of the two special names terminal and default.

Note that this type check does not verify that a given string refers to an existing file.  Nor does it determine whether a string may validly represent a file on the current operating system.

$\mathrm{type}\left(''foobar''\,'\mathrm{filename}'\right)$

$\mathrm{true}$

$\mathrm{type}\left(\mathrm{terminal}\,'\mathrm{filename}'\right)$

$\mathrm{true}$

$\mathrm{type}\left(\mathrm{default}\,'\mathrm{filename}'\right)$

$\mathrm{true}$

$\mathrm{type}\left(\mathrm{foobar}\,'\mathrm{filename}'\right)$

$\mathrm{false}$