unifdef - Removes #ifdefed lines
unifdef [-tlc] [-Dsymbol] [-idsymbol] [-iusymbol] [file] [-Usymbol]
command partially simulates the behavior
of the C preprocessor in processing
Complements the action of
lines that would normally be removed and removes lines that would normally
as a defined
Specifies defined lines inside certain
to be ignored but copied out.
Specifies undefined lines inside certain
to be ignored and not copied out.
Replaces removed lines with blank lines instead of deleting
Processes plain text (rather than C code) input. The
command does not try to recognize comments, single quotes,
and double quotes.
as an undefined
The unifdef command recognizes nested #ifdefs, comments, single and double quotes of C syntax so that it can function correctly, but does not include files or interpret macros. The unifdef command recognizes, but does not remove comments.
The unifdef command takes its input from stdin if no file argument is given, and copies its output to stdout.
You specify the symbols you want defined with -Dsymbol or undefined with -Usymbol and the lines inside those #ifdefs are copied to the output or removed, as appropriate. The #ifdef, #ifndef, #else, #elif, and endif lines associated with symbol are also removed. The #ifdefs involving unspecified symbols are untouched and copied out along with their associated #ifdef, #else, elif, and #endif lines. If the same symbol appears in more than one argument, only the first occurrence is significant. For instance, if an #ifdef X occurs nested inside another #ifdef X, the inside #ifdef is considered an unrecognized symbol.
If you use
#ifdefs to delimit non-C lines, such as
comments or unfinished code, it is necessary to specify which symbols are
to be used for that purpose. Otherwise, the
tries to parse for quotes and comments in those
The following keywords can be used with the unifdef command:
ifdef ifndef else endif elif
The unifdef command uses the elif keyword as follows. (Note that ``Understood'' means unifdef knows how to convert elif to if.) Understood Not understood Not understood
# ifdef X x # elif defined (Y) y # elif defined (A) || defined (B) a # else default # endif
The following list shows the results of using the elif keyword with variables:
-UX # if defined (Y) y # elif defined (A) || defined (B) a # else default # endif -UX -DY y
-UY -UX # if defined (Y) y # elif defined (A) || defined (B) a # else default # endif
-UY -UX -DA # if defined (Y) y # elif defined (A) || defined (B) a # else default # endif
The unifdef command cannot process cpp constructs such as:
#if defined(X) || defined(Y)
command can fail for several reasons:
a premature end of file, or an inappropriate
Exit status is 0 if output is an exact copy of input, 1 if not, 2 if
The following command line causes the unifdef command to read the file original.c and remove the #ifdef A lines. It then removes everything following an #elif/#else associated with the #ifdef A down to the #endif: unifdef -DA original.c > modified.c The following command line causes the unifdef command to read the file original.c, and remove the #ifdef A down to either its associated #elif/#else, or its associated #endif: unifdef -UA original.c > modified.c