plan9 man page for diff

DIFF(1) 						      General Commands Manual							   DIFF(1)

NAME
       diff - differential file comparator

SYNOPSIS
       diff [ -efbwr ] file1 ... file2

DESCRIPTION
       Diff tells what lines must be changed in two files to bring them into agreement.  If one file is a directory, then a file in that directory
       with basename the same as that of the other file is used.  If both files are directories, similarly named files in the two directories  are
       compared  by the method of diff for text files and cmp(1) otherwise.  If more than two file names are given, then each argument is compared
       to the last argument as above.  The -r option causes diff to process similarly named subdirectories recursively.  The  normal  output  con-
       tains lines of these forms:

	    n1 a n3,n4
	    n1,n2 d n3
	    n1,n2 c n3,n4

       These  lines resemble ed commands to convert file1 into file2.  The numbers after the letters pertain to file2.	In fact, by exchanging `a'
       for `d' and reading backward one may ascertain equally how to convert file2 into file1.	As in ed, identical pairs where n1 = n2 or n3 = n4
       are abbreviated as a single number.

       Following  each	of these lines come all the lines that are affected in the first file flagged by `<', then all the lines that are affected
       in the second file flagged by `>'.

       The -b option causes trailing blanks (spaces and tabs) to be ignored and other strings of blanks to compare equal.  The	-w  option  causes
       all white-space to be removed from input lines before applying the difference algorithm.

       The  -e	option produces a script of a, c and d commands for the editor ed, which will recreate file2 from file1.  The -f option produces a
       similar script, not useful with ed, in the opposite order. It may, however, be useful as input to a stream-oriented post-processor.

       Except in rare circumstances, diff finds a smallest sufficient set of file differences.

FILES
       /tmp/diff[12]

SOURCE
       /sys/src/cmd/diff

SEE ALSO
       cmp(1), ed(1)

DIAGNOSTICS
       Exit status is the empty string for no differences, for some, and for trouble.

BUGS
       Editing scripts produced under the -e or -f option are naive about creating lines consisting of a single `.'.
       When running diff on directories, the notion of what is a text file is open to debate.

																	   DIFF(1)