DIFF(1) COMMAND REFERENCE DIFF(1) NAME diff - differential file and directory comparator SYNOPSIS diff [-l] [-r] [-s] [-Sfilename] [-{c,e,f,h}] [-b] dir1 dir2 diff [-{c,e,f,h}] [-b] file1 file2 diff [-Dstring] [-b] file1 file2 DESCRIPTION In the first form of the command line, diff sorts the contents of the directories by name, and then runs the regular file diff algorithm (described below) on text files which are different. Binary files which differ, common subdirectories, and files which appear in only one directory are listed. In the second and third forms, and when comparing text files which differ during directory comparison, 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 file differences. If neither file1 nor file2 is a directory, then either may be given as `-', in which case the standard input is used. If file1 is a directory, then a file in that directory whose file-name is the same as the file-name of file2 is used (and vice versa). There are several options for output format; the default output format contains 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 `>'. OPTIONS Options when comparing directories are: -l Long output format; each text file diff is piped through pr(1) to paginate it, other differences are remembered and summarized after all text file differences are reported. Printed 5/12/88 1
DIFF(1) COMMAND REFERENCE DIFF(1) -r Causes application of diff recursively to common subdirectories encountered. -s Causes diff to report files which are the same, which are otherwise not mentioned. -Sfilename Starts a directory diff in the middle beginning with filename. Except for -b, which may be given with any of the others, the following options are mutually exclusive: -b Causes trailing blanks (spaces and tabs) to be ignored, and other strings of blanks to compare equal. -c Produces a diff with lines of context. The default is to present 3 lines of context and may be changed, e.g to 10, by -c10. With -c the output format is modified slightly: the output beginning with identification of the files involved and their creation dates and then each change is separated by a line with a dozen *'s. The 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 `!'. -e Produces a script of a, c and d commands for the editor ed, which will recreate file2 from file1. In connection with -e, the following shell program may help maintain multiple versions of a file. Only an ancestral file ($1) and a chain of version-to-version ed scripts ($2,$3,...) made by diff need be on hand. A `latest version' appears on the standard output. (shift; cat $*; echo '1,$p') | ed - $1 Extra commands are added to the output when comparing directories with -e, so that the result is a sh(1sh) script for converting text files which are common to the two directories from their state in dir1 to their state in dir2. -f Produces a script similar to that of -e, not useful with ed, and in the opposite order. -h Does a fast, half-hearted job. It works only when changed stretches are short and well separated, but does work on files of unlimited length. Only recognizes the -b option. All other options are ignored. -Dstring Causes diff to create a merged version of file1 and file2 Printed 5/12/88 2
DIFF(1) COMMAND REFERENCE DIFF(1) on the standard output, with C preprocessor controls included so that a compilation of the result without defining string is equivalent to compiling file1, while defining string will yield file2. EXAMPLES The following invocation performs the difference function on the files pgm.version1 and pgm.version2. The results are written on standard output. diff pgm.version1 pgm.version2 FILES /tmp/d????? Temporary files /usr/lib/diffh half-hearted (-h) diff function RETURN VALUE [0] No differences. [1] There are differences. [USAGE] Incorrect command line syntax. Execution terminated. [NP_WARN] An error warranting a warning message occurred. Execution continues. [NP_ERR] An error occurred that was not a system error. Execution terminated. [P_WARN] A system error occurred. Execution continues. See intro(2) for more information on system errors. [P_ERR] A system error occurred. Execution terminated. See intro(2) for more information on system errors. [INTERNAL] An unexpected error occurred. Execution was terminated. Record the message and save the core file for analysis. Contact service personnel at your Tektronix field office. CAVEATS Editing scripts produced under the -e or -f option are naive about creating lines consisting of a single `.'. When comparing directories with the -b option specified, diff first compares the files ala cmp(1), and then decides to run the diff algorithm if they are not equal. This may Printed 5/12/88 3
DIFF(1) COMMAND REFERENCE DIFF(1) cause a small amount of spurious output if the files then turn out to be identical because the only differences are insignificant blank string differences. SEE ALSO cmp(1), cc(1), comm(1), ed(1), diff3(1), and pr(1). Printed 5/12/88 4
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