Diff - Unix application

Diff is a unix application created in 1974.

#412on PLDB

50Years Old

In computing, the diff utility is a data comparison tool that calculates and displays the differences between two 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 diff command displays the changes made in a standard format, such that both humans and machines can understand the changes and apply them: given one file and the changes, the other file can be created. Read more on Wikipedia...

Diff Wikipedia page
Diff first developed in AT&T Bell Laboratories
file extensions for Diff include diff and patch
The Google BigQuery Public Dataset GitHub snapshot shows 477 users using Diff in 561 repos on GitHub
CodeMirror package for syntax highlighting Diff
Pygments supports syntax highlighting for Diff
GitHub supports syntax highlighting for Diff
See also: (15 related languages)Unix, grep, Emacs, Regular Expressions, C, Bourne shell, Fortran, Modula-2, Lisp, ISBN, DOI, ed script, patch, Context Diff, Unified Diff

Example from Linguist:

diff --git a/lib/linguist.rb b/lib/linguist.rb
index d472341..8ad9ffb 100644
--- a/lib/linguist.rb
+++ b/lib/linguist.rb

Example from Wikipedia:

--- /path/to/original	timestamp
+++ /path/to/new	timestamp
@@ -1,3 +1,9 @@
+This is an important
+notice! It should
+therefore be located at
+the beginning of this
+document!
+
 This part of the
 document has stayed the
 same from version to
@@ -5,16 +11,10 @@
 be shown if it doesn't
 change.  Otherwise, that
 would not be helping to
-compress the size of the
-changes.
-
-This paragraph contains
-text that is outdated.
-It will be deleted in the
-near future.
+compress anything.

 It is important to spell
-check this dokument. On
+check this document. On
 the other hand, a
 misspelled word isn't
 the end of the world.
@@ -22,3 +22,7 @@
 this paragraph needs to
 be changed. Things can
 be added after it.
+
+This paragraph contains
+important new additions
+to this document.