Diff

This article is about the utility program. For the general topic of file comparison, see File comparison. For diffs in Wikipedia, see Help:Diff. For other uses, see DIFF.
diff
Original author(s)Douglas McIlroy
(AT&T Bell Laboratories)
Developer(s)Various open-source and commercial developers
Initial releaseJune 1974; 50 years ago (1974-06)
Written inC
Operating systemUnix, Unix-like, V, Plan 9, Inferno
PlatformCross-platform
TypeCommand
LicensePlan 9: MIT License

In computing, the utility diff is a data comparison tool that computes and displays the differences between the contents of files. Unlike edit distance notions used for other purposes, diff is line-oriented rather than character-oriented, but it is like Levenshtein distance in that it tries to determine the smallest set of deletions and insertions to create one file from the other. The utility displays the changes in one of several standard formats, such that both humans or computers can parse the changes, and use them for patching.

Typically, diff is used to show the changes between two versions of the same file. Modern implementations also support binary files.[1] The output is called a "diff", or a patch, since the output can be applied with the Unix program patch. The output of similar file comparison utilities is also called a "diff"; like the use of the word "grep" for describing the act of searching, the word diff became a generic term for calculating data difference and the results thereof.[2] The POSIX standard specifies the behavior of the "diff" and "patch" utilities and their file formats.[3]

  1. ^ MacKenzie et al. "Binary Files and Forcing Text Comparison" in Comparing and Merging Files with GNU Diff and Patch. Downloaded 28 April 2007. [1] Archived 2017-12-19 at the Wayback Machine
  2. ^ Eric S. Raymond (ed.), "diff" Archived 2014-01-31 at the Wayback Machine, The Jargon File, version 4.4.7
  3. ^ IEEE Computer Society; The Open Group (26 September 2008). Standard for Information Technology—Portable Operating System Interface (POSIX) Base Specifications, Issue 7. pp. 2599–2607. IEEE Std. 1003.1-2001 specifies traditional, "ed script", and context diff output formats; IEEE Std. 1003.1-2008 added the (by then more common) unified format.