NAME
unifdef - remove ifdef’ed lines

SYNOPSIS
unifdef [ -t -l -c -Dsym -Usym -idsym -iusym ] ... [ file ]

DESCRIPTION
Unifdef is useful for removing ifdef’ed lines from a file while
otherwise leaving the file alone. Unifdef is like a stripped-down
C preprocessor: it is smart enough to deal with the nested ifdefs,
comments, single and double quotes of C syntax so that it can do
its job, but it doesn’t do any including or interpretation of
macros. Neither does it strip out comments, though it recognizes
and ignores them. You specify which symbols you want defined -Dsym
or undefined -Usym and the lines inside those ifdefs will be copied
to the output or removed as appropriate. The ifdef, ifndef, else,
and endif lines associated with sym will also be removed. Ifdefs
involving symbols you don’t specify are untouched and copied out
along with their associated ifdef, else, and endif lines. If an
ifdef X occurs nested inside another ifdef X, then the inside ifdef
is treated as if it were an unrecognized symbol. If the same
symbol appears in more than one argument, only the first occurrence
is significant.

The -l option causes unifdef to replace removed lines with blank
lines instead of deleting them.

If you use ifdefs to delimit non-C lines, such as comments or code
which is under construction, then you must tell unifdef which
symbols are used for that purpose so that it won’t try to parse for
quotes and comments in those ifdef’ed lines. You specify that you
want the lines inside certain ifdefs to be ignored but copied out
with -idsym and -iusym similar to -Dsym and -Usym above.

If you want to use unifdef for plain text (not C code), use the -t
option. This makes unifdef refrain from attempting to recognize
comments and single and double quotes.

Unifdef copies its output to stdout and will take its input from
stdin if no file argument is given. If the -c argument is
specified, then the operation of unifdef is complemented, i.e. the
lines that would have been removed or blanked are retained and vice
versa.