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	diff.1 - 9base - revived minimalist port of Plan 9 userland to Unix
	git clone git://git.suckless.org/9base
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	diff.1 (2959B)
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	1 .TH DIFF 1
	2 .SH NAME
	3 diff \- differential file comparator
	4 .SH SYNOPSIS
	5 .B diff
	6 [
	7 .B -acefmnbwr
	8 ] file1 ... file2
	9 .SH DESCRIPTION
	10 .I Diff
	11 tells what lines must be changed in two files to bring them
	12 into agreement.
	13 If one file
	14 is a directory,
	15 then a file in that directory with basename the same as that of
	16 the other file is used.
	17 If both files are directories, similarly named files in the
	18 two directories are compared by the method of
	19 .I diff
	20 for text
	21 files and
	22 .IR cmp (1)
	23 otherwise.
	24 If more than two file names are given, then each argument is compared
	25 to the last argument as above.
	26 The
	27 .B -r
	28 option causes
	29 .I diff
	30 to process similarly named subdirectories recursively.
	31 When processing more than one file,
	32 .I diff
	33 prefixes file differences with a single line
	34 listing the two differing files, in the form of
	35 a
	36 .I diff
	37 command line.
	38 The
	39 .B -m
	40 flag causes this behavior even when processing single files.
	41 .PP
	42 The normal output contains lines of these forms:
	43 .IP "" 5
	44 .I n1
	45 .B a
	46 .I n3,n4
	47 .br
	48 .I n1,n2
	49 .B d
	50 .I n3
	51 .br
	52 .I n1,n2
	53 .B c
	54 .I n3,n4
	55 .PP
	56 These lines resemble
	57 .I ed
	58 commands to convert
	59 .I file1
	60 into
	61 .IR file2 .
	62 The numbers after the letters pertain to
	63 .IR file2 .
	64 In fact, by exchanging `a' for `d' and reading backward
	65 one may ascertain equally how to convert
	66 .I file2
	67 into
	68 .IR file1 .
	69 As in
	70 .IR ed ,
	71 identical pairs where
	72 .I n1
	73 =
	74 .I n2
	75 or
	76 .I n3
	77 =
	78 .I n4
	79 are abbreviated as a single number.
	80 .PP
	81 Following each of these lines come all the lines that are
	82 affected in the first file flagged by `<',
	83 then all the lines that are affected in the second file
	84 flagged by `>'.
	85 .PP
	86 The
	87 .B -b
	88 option causes
	89 trailing blanks (spaces and tabs) to be ignored
	90 and other strings of blanks to compare equal.
	91 The
	92 .B -w
	93 option causes all white-space to be removed from input lines
	94 before applying the difference algorithm.
	95 .PP
	96 The
	97 .B -n
	98 option prefixes each range with
	99 .IB file : \fR
	100 and inserts a space around the
	101 .BR a ,
	102 .BR c ,
	103 and
	104 .B d
	105 verbs.
	106 The
	107 .B -e
	108 option produces a script of
	109 .I "a, c"
	110 and
	111 .I d
	112 commands for the editor
	113 .IR ed ,
	114 which will recreate
	115 .I file2
	116 from
	117 .IR file1 .
	118 The
	119 .B -f
	120 option produces a similar script,
	121 not useful with
	122 .IR ed ,
	123 in the opposite order. It may, however, be
	124 useful as input to a stream-oriented post-processor.
	125 .PP
	126 The
	127 .B -c
	128 option includes three lines of context around each
	129 change, merging changes whose contexts overlap.
	130 The
	131 .B -a
	132 flag displays the entire file as context.
	133 .PP
	134 Except in rare circumstances,
	135 .I diff
	136 finds a smallest sufficient set of file
	137 differences.
	138 .SH FILES
	139 .B /tmp/diff[12]
	140 .SH SOURCE
	141 .B \*9/src/cmd/diff
	142 .SH "SEE ALSO"
	143 .IR cmp (1),
	144 .IR comm (1),
	145 .IR ed (1)
	146 .SH DIAGNOSTICS
	147 Exit status is the empty string
	148 for no differences,
	149 .L some
	150 for some,
	151 and
	152 .L error
	153 for trouble.
	154 .SH BUGS
	155 Editing scripts produced under the
	156 .BR -e " or"
	157 .BR -f " option are naive about"
	158 creating lines consisting of a single `\fB.\fR'.
	159 .PP
	160 When running
	161 .I diff
	162 on directories, the notion of what is a text
	163 file is open to debate.