.TH DIFF 1 .CT 1 files .SH NAME diff, diff3 \- differential file comparison .SH SYNOPSIS .B diff [ .I option ... ] .I file1 file2 .PP .B diff3 [ .B \-ex3 ] .I file1 file2 file3 .SH DESCRIPTION When run on regular files .I diff tells what lines must be changed in the files to bring them into agreement. Except in rare circumstances, .I diff finds a smallest sufficient set of differences. If neither file is a directory, then one may be .LR - , meaning the standard input. If one file is a directory, then a file in that directory with basename the same as that of the other file is used. .PP If both files are directories, similarly named files in the two directories are compared by the method of .I diff for text files and .IR cmp (1) otherwise. Options when comparing directories are: .TP .B -r Apply .I diff recursively to similarly named subdirectories. .TP .B -s Report files that are the same (normally not mentioned). .PP There are several options for output format; the default output format contains lines of these forms: .IP .IB n1 a .IB n3 , n4 .br .IB n1 , n2 d .I n3 .br .IB n1 , n2 c .IB n3 , n4 .PP These lines resemble .I ed commands to convert .I file1 into .IR file2 . The numbers after the letters pertain to .IR file2 . In fact, by exchanging .L a for .L d and reading backward one may ascertain equally how to convert .I file2 into .IR file1 . As in .I ed, identical pairs where .IR n1 = n2 or .I n3 = n4 are abbreviated as a single number. .PP Following each of these lines come all the lines that are affected in the first file flagged by .LR < , then all the lines that are affected in the second file flagged by .LR > . .PP Except for .B -b, which may be given with any of the others, the following options are mutually exclusive: .TP .B -e Produce a script of .LR a , .LR c , and .L d for .IR ed (1) to recreate .I file2 from .IR file1 . When comparing directories, produce a .IR sh (1) script to convert text files common to the two directories. .TP .BI -c n Include .I n extra lines of context with each set of differences. The output format is modified: the output begins with identification of the files involved and their creation dates and changes are separated by lines of *'s. Lines removed from .I file1 are marked with .LR - ; those added to .I file2 are marked .LR + . Lines which are changed from one file to the other are marked in both files with .LR ! . .TP .B -h Do a fast, half-hearted job, useful only when changed stretches are short and well separated, but does work on files of unlimited length. .TP .B -b Ignore trailing blanks (spaces and tabs) and treat other strings of blanks as if they were a single space. .PP .I Diff3 compares three versions of a file and publishes the various disagreeing ranges of text. One of the following indicators introduces each reported difference. .TP .B ==== All three files differ. .TP .BI ==== f File .I f differs, where .I f is 1, 2, or 3. .PP Disagreeing fragments from the three files follow the .B ==== line, each identified by a .IR diff -like range indication: .TP .IB f : n1 a File .I f lacks text that other files have; their text would be appended after line .I n1. .TP .IB f : n1 , n2 c .br .ns .TP .IB f : n1 c Lines .I n1 through .I n2 (or line .I n1 only) of file .I f would have to be changed to agree with some other file. The original contents follow, unless a higher-numbered file has the same contents. .PP Under option .BR -e , .I diff3 publishes a script for .IR ed (1) that will incorporate into .I file1 all changes between .I file2 and .I file3, i.e. the changes that normally would be flagged .B ==== and .BR ====3 . Option .B \-x (\fB\-3\fR) produces a script to incorporate only changes flagged .B ==== .RB ( ====3 ). .SH EXAMPLES .TP .L (cat diff0-1 diff1-2 diff2-3; echo '1,$p') | ed - file0 >file3 An ancestral .L file0 has been kept along with a chain of version-to-version difference files made thus: .LR "diff -e file0 file1 >diff0-1" . The shell command reconstructs the latest version. .PP .EX if diff3 mod1 old mod2 | grep -s '^====$' then : else (diff3 -e mod1 old mod2; echo '1,$p') | ed - mod1 >new fi .EE .PD0 .IP Compare two different modified versions with an old file. If no modifications interfere with each other .RI ( grep finds no .B ==== lines), make a new file incorporating both modifications. .PD .SH FILES .F /tmp/d* .br .F /usr/lib/diffh for .B -h .br .F /usr/lib/diff3 .SH "SEE ALSO" .IR cmp (1), .IR comm (1), .IR ed (1), .IR idiff (1) .SH DIAGNOSTICS .I Diff yields exit status is 0 for no differences, 1 for some, 2 for trouble. .SH BUGS Text lines that consist of a single `.' will defeat options .BR -e , .BR -x , and .BR -3 . .br Superfluous output may result for files that differ only in insignificant blanks when comparing directories under option .BR -b . .br Option .B -c is superfluous.