groff: Troff and Nroff Mode
5.12 Troff and Nroff Mode
=========================
Originally, 'nroff' and 'troff' were two separate programs, the former
for TTY output, the latter for everything else. With GNU 'troff', both
programs are merged into one executable, sending its output to a device
driver ('grotty' for TTY devices, 'grops' for POSTSCRIPT, etc.) which
interprets the intermediate output of 'gtroff'. For UNIX 'troff' it
makes sense to talk about "Nroff mode" and "Troff mode" since the
differences are hardcoded. For GNU 'troff', this distinction is not
appropriate because 'gtroff' simply takes the information given in the
font files for a particular device without handling requests specially
if a TTY output device is used.
Usually, a macro package can be used with all output devices.
Nevertheless, it is sometimes necessary to make a distinction between
TTY and non-TTY devices: 'gtroff' provides two built-in conditions 'n'
and 't' for the 'if', 'ie', and 'while' requests to decide whether
'gtroff' shall behave like 'nroff' or like 'troff'.
-- Request: .troff
Make the 't' built-in condition true (and the 'n' built-in
condition false) for 'if', 'ie', and 'while' conditional requests.
This is the default if 'gtroff' (_not_ 'groff') is started with the
'-R' switch to avoid loading of the start-up files 'troffrc' and
'troffrc-end'. Without '-R', 'gtroff' stays in troff mode if the
output device is not a TTY (e.g. 'ps').
-- Request: .nroff
Make the 'n' built-in condition true (and the 't' built-in
condition false) for 'if', 'ie', and 'while' conditional requests.
This is the default if 'gtroff' uses a TTY output device; the code
for switching to nroff mode is in the file 'tty.tmac', which is
loaded by the start-up file 'troffrc'.
Conditionals and Loops, for more details on built-in
conditions.
Info Catalog
groff: Character Translations
groff: gtroff Reference
groff: Line Layout