TMPDIR is the canonical environment variable in Unix and POSIX[1] that should be used to specify a temporary directory for scratch space.
Most Unix programs will honor this setting and use its value to denote the scratch area for temporary files instead of the common default of /tmp[2][3] or /var/tmp.
[4] Other forms sometimes accepted are TEMP, TEMPDIR and TMP, but these alternatives are used more commonly by non-POSIX operating systems or non-conformant programs.
TMPDIR is specified in various Unix and similar standards, e.g. per the Single UNIX Specification.
This Unix-related article is a stub.