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Annotation of lucent/sys/man/1/diff, revision 1.1.1.1

1.1       root        1: .TH DIFF 1 
                      2: .SH NAME
                      3: diff \- differential file comparator
                      4: .SH SYNOPSIS
                      5: .B diff
                      6: [
                      7: .B -efbwr
                      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: The normal output contains lines of these forms:
                     32: .IP "" 5
                     33: .I n1
                     34: .B a
                     35: .I n3,n4
                     36: .br
                     37: .I n1,n2
                     38: .B d
                     39: .I n3
                     40: .br
                     41: .I n1,n2
                     42: .B c
                     43: .I n3,n4
                     44: .PP
                     45: These lines resemble
                     46: .I ed
                     47: commands to convert
                     48: .I file1
                     49: into
                     50: .IR file2 .
                     51: The numbers after the letters pertain to
                     52: .IR file2 .
                     53: In fact, by exchanging `a' for `d' and reading backward
                     54: one may ascertain equally how to convert 
                     55: .I file2
                     56: into
                     57: .IR file1 .
                     58: As in 
                     59: .IR ed ,
                     60: identical pairs where
                     61: .I n1
                     62: =
                     63: .I n2
                     64: or
                     65: .I n3
                     66: =
                     67: .I n4
                     68: are abbreviated as a single number.
                     69: .PP
                     70: Following each of these lines come all the lines that are
                     71: affected in the first file flagged by `<', 
                     72: then all the lines that are affected in the second file
                     73: flagged by `>'.
                     74: .PP
                     75: The
                     76: .B -b
                     77: option causes
                     78: trailing blanks (spaces and tabs) to be ignored
                     79: and other strings of blanks to compare equal.
                     80: The
                     81: .B -w
                     82: option causes all white-space to be removed from input lines
                     83: before applying the difference algorithm.
                     84: .PP
                     85: The
                     86: .B -e
                     87: option produces a script of
                     88: .I "a, c"
                     89: and 
                     90: .I d
                     91: commands for the editor
                     92: .IR ed ,
                     93: which will recreate
                     94: .I file2
                     95: from
                     96: .IR file1 .
                     97: The
                     98: .B -f
                     99: option produces a similar script,
                    100: not useful with
                    101: .IR ed ,
                    102: in the opposite order. It may, however, be
                    103: useful as input to a stream-oriented post-processor.
                    104: .PP
                    105: Except in rare circumstances,
                    106: .I diff
                    107: finds a smallest sufficient set of file
                    108: differences.
                    109: .SH FILES
                    110: .B /tmp/diff[12]
                    111: .SH SOURCE
                    112: .B /sys/src/cmd/diff
                    113: .SH "SEE ALSO"
                    114: .IR cmp (1),
                    115: .IR ed (1)
                    116: .SH DIAGNOSTICS
                    117: Exit status is the empty string
                    118: for no differences,
                    119: .L some
                    120: for some, 
                    121: and
                    122: .L error
                    123: for trouble.
                    124: .SH BUGS
                    125: Editing scripts produced under the
                    126: .BR -e " or"
                    127: .BR -f " option are naive about"
                    128: creating lines consisting of a single `\fB.\fR'.
                    129: .br
                    130: When running
                    131: .I diff
                    132: on directories, the notion of what is a text
                    133: file is open to debate.

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