~user	Expands the the home directory of user
~	Expands the the current user's home ($HOME)
$var	Expands to pce<-environment_variable

pce<-environment_variable is an interface to Unix getenv, but the variable PCEHOME is expanded to PCE's home directory even if it does not exists in the Unix environment.

This class may be used to create a temporary file by omiting path. On systems providing mkstemp(), this function is used to generate a unique file in $TMPDIR or /tmp that is immediately opened for write and not accessible for other users. For compatibility, the file object gets the status tmp_write. A subsequent file->open in mode write or append simply sets the status to write. On other systems, tmpnam() is used to generate the filename. The mkstemp() approach is preferred for security reasons as it avoids race-conditions and access by others than the current user.

The encoding argument specifies whether the file contains an octed stream or a stream of character codes. See source_sink->encoding for details on character encoding issues.