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DIFF(1) General Commands Manual DIFF(1) NAME diff, diff3 - differential file comparison SYNOPSIS diff [ option ... ] file1 file2 diff3 [ -ex3 ] file1 file2 file3 DESCRIPTION When run on regular files diff tells what lines must be changed in the files to bring them into agreement. Except in rare circumstances, diff finds a smallest sufficient set of differences. If neither file is a directory, then one may be 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. If both files are directories, similarly named files in the two direc- tories are compared by the method of diff for text files and cmp(1) otherwise. Options when comparing directories are: -r Apply diff recursively to similarly named subdirectories. -s Report files that are the same (normally not mentioned). There are several options for output format; the default output format contains lines of these forms: n1a n3,n4 n1,n2d n3 n1,n2c n3,n4 These lines resemble ed commands to convert file1 into file2. The num- bers after the letters pertain to file2. In fact, by exchanging for 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 ab- breviated 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 -e Produce a script of and for ed(1) to recreate file2 from file1. When comparing directories, produce a sh(1) script to convert text files common to the two directories. -cn Include n extra lines of context with each set of differences. The output format is modified: the output begins with identifi- cation of the files involved and their creation dates and changes are separated by lines of *'s. Lines removed from file1 are marked with those added to file2 are marked Lines which are changed from one file to the other are marked in both files with -h Do a fast, half-hearted job, useful only when changed stretches are short and well separated, but does work on files of unlim- ited length. -b Ignore trailing blanks (spaces and tabs) and treat other strings of blanks as if they were a single space. -B Ignore all blanks. Diff3 compares three versions of a file and publishes the various dis- agreeing ranges of text. One of the following indicators introduces each reported difference. ==== All three files differ. ====f File f differs, where f is 1, 2, or 3. Disagreeing fragments from the three files follow the ==== line, each identified by a diff-like range indication: f:n1a File f lacks text that other files have; their text would be ap- pended after line n1. f:n1,n2c f:n1c Lines n1 through n2 (or line n1 only) of file 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. Under option -e, diff3 publishes a script for ed(1) that will incorpo- rate into file1 all changes between file2 and file3, i.e. the changes that normally would be flagged ==== and ====3. Option -x (-3) produces a script to incorporate only changes flagged ==== (====3). EXAMPLES (cat diff0-1 diff1-2 diff2-3; echo '1,$p') | ed - file0 >file3 An ancestral has been kept along with a chain of version-to-ver- sion difference files made thus: The shell command reconstructs the latest version. if diff3 mod1 old mod2 | grep -s '^====$' then : else (diff3 -e mod1 old mod2; echo '1,$p') | ed - mod1 >new fi Compare two different modified versions with an old file. If no modifications interfere with each other (grep finds no ==== lines), make a new file incorporating both modifications. FILES for -h SEE ALSO cmp(1), comm(1), ed(1), idiff(1) DIAGNOSTICS Diff yields exit status is 0 for no differences, 1 for some, 2 for trouble. BUGS Text lines that consist of a single `.' will defeat options -e, -x, and -3. Superfluous output may result for files that differ only in insignifi- cant blanks when comparing directories under option -b. Option -c is unpardonably bizarre. DIFF(1)