There are also several environment variables (of the operating system,
not within `gtroff') which can modify the behavior of `groff'.
If this is set to X, then `groff' runs `Xtroff' instead of
`gtroff'. This also applies to `tbl', `pic', `eqn', `grn',
`refer', and `soelim'. It does not apply to `grops', `grodvi',
`grotty', `pre-grohtml', `post-grohtml', `grolj4', and `gxditview'.
The default command prefix is determined during the installation
process. If a non-GNU troff system is found, prefix `g' is used,
A colon-separated list of directories in which to search for macro
files (before the default directories are tried). Note: Macro
The default output device.
A colon-separated list of directories in which to search for the
`dev'NAME directory (before the default directories are tried).
Note: Font Directories.
This search path, followed by `PATH', is used for commands executed
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.
Note that MS-DOS and MS-Windows ports of `groff' use semi-colons,
rather than colons, to separate the directories in the lists described
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