NAME

     ifdef - remove #ifdefs from a file


SYNOPSIS

     ifdef  [-t]  [-dsymbol]  [-Dsymbol]  [-Usymbol]   [-Isymbol]
     [file]


OPTIONS

     -D   Define symbol permanently

     -I   Ignore symbol

     -U   Undefine symbol permanently

     -d   Define symbol. It may be #undef'ed later

     -t   Produce a table of the symbols on stdout


EXAMPLES

     ifdef -DUNIX file.c >newfile.c
                         # Define UNIX

     ifdef -D_MINIX -UDOS <x.c >y.c
                         # Define


DESCRIPTION

     Ifdef allows conditional code [ #ifdef ... #endif  ]  to  be
     selectively removed from C files, but at the same time leav-
     ing  all  other  C  preprocessor  commands  intact  such  as
     #define,  #include  etc.   Input to ifdef is either the file
     named as the last argument, or stdin if no  file  is  named.
     Output goes to stdout.

     Symbols may be defined with the -d or  -D  flags  just  like
     cpp,  except  that  the  latter  option  ignores  subsequent
     #undefs.  It is not permitted to  give  values  to  symbols.
     Similarly,  -U  undefines  a  symbol  and ignores subsequent
     #definess.  Symbols defined with -I are ignored; any  #ifdef
     using an ignored symbol will be left intact.