Info Catalog diffutils: Scripts diffutils: Output Formats

diffutils: If-then-else

 
 2.6 Merging Files with If-then-else
 ===================================
 
 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.
 

Menu

 
· Line Group Formats    Formats for general if-then-else line groups.
· Line Formats          Formats for each line in a line group.
· Example If-then-else  Sample if-then-else format output.
· Detailed If-then-else A detailed description of if-then-else format.
 

Info Catalog diffutils: Scripts diffutils: Output Formats