You can use diff
to merge two files of C source code. The output
of diff
in this format contains all the lines of both files.
Lines common to both files are output just once; the differing parts are
separated by the C preprocessor directives #ifdef name
or
#ifndef name
, #else
, and #endif
. When
compiling the output, you select which version to use by either defining
or leaving undefined the macro name.
To merge two files, use diff
with the `-D name' or
`--ifdef=name' option. The argument name is the C
preprocessor identifier to use in the #ifdef
and #ifndef
directives.
For example, if you change an instance of wait (&s)
to
waitpid (-1, &s, 0)
and then merge the old and new files with
the `--ifdef=HAVE_WAITPID' option, then the affected part of your code
might look like this:
do { #ifndef HAVE_WAITPID if ((w = wait (&s)) < 0 && errno != EINTR) #else /* HAVE_WAITPID */ if ((w = waitpid (-1, &s, 0)) < 0 && errno != EINTR) #endif /* HAVE_WAITPID */ return w; } while (w != child);
You can specify formats for languages other than C by using line group formats and line formats, as described in the next sections.
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