第 5 章 Preparing software for RPM packaging

Procedure

1. Back up the original source code:

   $ cp -p cello.c cello.c.orig

   The -p option preserves mode, ownership, and timestamps.

2. Modify cello.c as needed:

   #include <stdio.h>
   
   int main(void) {
       printf("Hello World from my very first patch!\n");
       return 0;
   }

3. Generate a patch:

   $ diff -Naur cello.c.orig cello.c
   --- cello.c.orig        2016-05-26 17:21:30.478523360 -0500
   + cello.c     2016-05-27 14:53:20.668588245 -0500
   @@ -1,6 +1,6 @@
    #include<stdio.h>
   
    int main(void){
   -    printf("Hello World!\n");
   +    printf("Hello World from my very first patch!\n");
        return 0;
    }
   \ No newline at end of file

   Lines that start with + replace the lines that start with -.

   注意

   Using the Naur options with the diff command is recommended because it fits the majority of use cases:

   • -N (--new-file)

     The -N option handles absent files as empty files.

   • -a (--text)

     The -a option treats all files as text. As a result, the diff utility does not ignore the files it classified as binaries.

   • -u (-U NUM or --unified[=NUM])

     The -u option returns output in the form of output NUM (default 3) lines of unified context. This is a compact and an easily readable format commonly used in patch files.

   • -r (--recursive)

     The -r option recursively compares any subdirectories that the diff utility found.

   However, note that in this particular case, only the -u option is necessary.

4. Save the patch to a file:

   $ diff -Naur cello.c.orig cello.c > cello.patch

5. Restore the original cello.c:

   $ mv cello.c.orig cello.c

   重要

   You must retain the original cello.c because the RPM package manager uses the original file, not the modified one, when building an RPM package. For more information, see Working with spec files.

1. Redirect the patch file to the patch command:

   $ patch < cello.patch
   patching file cello.c

2. Check that the contents of cello.c now reflect the desired change:

   $ cat cello.c
   #include<stdio.h>
   
   int main(void){
       printf("Hello World from my very first patch!\n");
       return 1;
   }

Verification

1. Build the patched cello.c program:

   $ make
   gcc -g -o cello cello.c

2. Run the built cello.c program:

   $ ./cello
   Hello World from my very first patch!