The Linux Development Platform Configuring, Using, and ... - Classes

CH07.fm Page 216 Monday, October 7, 2002 9:12 PM
216 Chapter 7 • Miscellaneous Tools
what changes have been made in the working copy of the file. The output of the diff utility follows
similar rules to those used in the CVS diff command. The following command shows
that files hello.c and hello.c~ are different at line number 11. The line starting with the
less-than symbol is taken from the first file (hello.c) and the line starting with the greaterthan
symbol is taken from the file hello.c~.
[root@boota]# diff hello.c hello.c~
11c11
< char string[30];
---
> char string[25];
[root@boota]#
The first line of the output contains the character c (changed) that shows that line 11 in the
first file is changed to line 11 in the second file.
You can also use “unified diff” that tells you additional information about the file
and displays a few lines before and after the lines that are different. See the following output of
the unified diff command:
[root@boota]# diff hello.c hello.c~ -u
--- hello.cTue Jun 25 14:43:30 2002
+++ hello.c~Tue Jun 25 14:43:38 2002
@@ -8,7 +8,7 @@
main ()
{
- char string[30];
+ char string[25];
printf ("Enter a line of characters : ");
scanf ("%s", string);
[root@boota]#
You can also use the –p option with the command to display the name of the function in
which the modified line(s) exist.
If you add a line after line 15 in hello.c file and run the diff command once again,
the result will be as follows:
[root@boota]# diff hello.c hello.c~
11c11
< char string[30];
---
> char string[25];
16d15
< printf ("End of program\n");
[root@boota]#