2.2 Environment

There are also several environment variables (of the operating system, not within gtroff) that can modify the behavior of groff.

GROFF_BIN_PATH

This search path, followed by PATH, is used for commands executed by groff.

GROFF_COMMAND_PREFIX

If this is set to X, then groff runs Xtroff instead of gtroff. This also applies to tbl, pic, eqn, grn, chem, refer, and soelim. It does not apply to grops, grodvi, grotty, pre-grohtml, post-grohtml, preconv, grolj4, gropdf, and gxditview.

The default command prefix is determined during the installation process. If a non-GNU troff system is found, prefix ‘g’ is used, none otherwise.

GROFF_ENCODING

The value of this variable is passed to the preconv preprocessor’s -e option to select the character encoding of input files. This variable’s existence implies the groff option -k. If set but empty, groff calls preconv without an -e option. groff’s -K option overrides GROFF_ENCODING. See the preconv(7) man page; type ‘man preconv’ at the command line to view it.

GROFF_FONT_PATH

A list of directories in which to seek the selected output device’s directory of device and font description files. GNU troff will search directories given as arguments to any specified -F options before these, and a built-in list of directories after them. See Font Directories and the troff(1) or gtroff(1) man pages.

GROFF_TMAC_PATH

A list of directories in which to seek macro files. GNU troff will search directories given as arguments to any specified -M options before these, and a built-in list of directories after them. See Macro Directories and the troff(1) or gtroff(1) man pages.

GROFF_TMPDIR

The directory in which groff creates temporary files. If this is not set and TMPDIR is set, temporary files are created in that directory. Otherwise temporary files are created in a system-dependent default directory (on Unix and GNU/Linux systems, this is usually /tmp). grops, grefer, pre-grohtml, and post-grohtml can create temporary files in this directory.

GROFF_TYPESETTER

Sets the default output device. If empty or not set, a build-time default (often ps) is used. The -Tdev option overrides GROFF_TYPESETTER.

SOURCE_DATE_EPOCH

A timestamp (expressed as seconds since the Unix epoch) to use as the output creation timestamp in place of the current time. The time is converted to human-readable form using localtime(3) when the formatter starts up and stored in registers usable by documents and macro packages (see Built-in Registers).

TZ

The time zone to use when converting the current time (or value of SOURCE_DATE_EPOCH) to human-readable form; see tzset(3).

MS-DOS and MS-Windows ports of groff use semicolons, rather than colons, to separate the directories in the lists described above.