This manual describes how to use GNU diff and patch to compare and merge files.
GNU diff and patch are free software. The term "free software" is sometimes misunderstood — it has nothing to do with price. It is about freedom. It refers to your freedom to run, copy, distribute, study, change and improve the software. With GNU diff and patch you have all these freedoms.
GNU diff and patch are part of the GNU Project. The GNU Project was launched in 1984 to develop a complete Unix-like operating system which is free software: the GNU system. It was conceived as a way of bringing back the cooperative spirit that prevailed in the computing community in earlier days. Its goal is to make cooperation possible once again by removing the obstacles to cooperation imposed by the owners of proprietary software. Variants of the GNU operating system, which use the kernel Linux, are now widely used; though these systems are often referred to as “Linux”, they are more accurately called GNU/Linux systems.
The Free Software Foundation is a tax-exempt charity that raises funds for work on the GNU Project. It is dedicated to promoting computer users’ right to use, study, copy, modify, and redistribute computer programs. You can support the Free Software Foundation by becoming an associate member — for more information visit the website www.gnu.org.