ifnames - Extract CPP conditionals from a set of files
ifnames [OPTION]... [FILE]...
Scan all of the C source FILES (or the standard input, if none are given) and write to the standard output a sorted list of all the identifiers that appear in those files in '#if', '#elif', '#ifdef', or '#ifndef' directives. Print each identifier on a line, followed by a space-separated list of the files in which that identifier occurs.
print this help, then exit
print version number, then exit
Written by David J. MacKenzie and Paul Eggert.
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This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law.
autoconf(1), automake(1), autoreconf(1), autoupdate(1), autoheader(1), autoscan(1), config.guess(1), config.sub(1), ifnames(1), libtool(1).
The full documentation for ifnames is maintained as a Texinfo manual. If the info and ifnames programs are properly installed at your site, the command
should give you access to the complete manual.