Last checked against version 2.5.4.
The patch program modifies a file according to a patch file. A patch file usually is a list created by the diff program that contains instructions on how an original file needs to be modified. Patch is used a lot for source code patches since it saves time and space. Imagine a package that is 1 MB in size. The next version of that package only has changes in two files of the first version. It can be shipped as an entirely new package of 1 MB or just as a patch file of 1 KB which will update the first version to make it identical to the second version. So if the first version was downloaded already, a patch file avoids a second large download.
Last checked against version 2.5.4.
Bash: sh
Binutils: as, ld
Diffutils: cmp
Fileutils: chmod, install, mv, rm
Gcc: cc, cc1, collect2, cpp0, gcc
Glibc: getconf
Grep: egrep, grep
Make: make
Sed: sed
Sh-utils: echo, expr, hostname, uname
Textutils: cat, tr