DIFF(1)                    OpenBSD Reference Manual                    DIFF(1)

NAME
     diff - differential file and directory comparator

SYNOPSIS
     diff [-abdilpTtw] [-c | -e | -f | -n | -q | -u] [-I pattern] [-L label]
          file1 file2
     diff [-abdilpTtw] [-I pattern] [-L label] -C number file1 file2
     diff [-abdiltw] [-I pattern] -D string file1 file2
     diff [-abdilpTtw] [-I pattern] [-L label] -U number file1 file2
     diff [-abdilNPprsTtw] [-c | -e | -f | -n | -q | -u] [-I pattern]
          [-L label] [-S name] [-X file] [-x pattern] dir1 dir2

DESCRIPTION
     The diff utility compares the contents of file1 and file2 and writes to
     the standard output the list of changes necessary to convert one file in-
     to the other.  No output is produced if the files are identical.

     Output options (mutually exclusive):

     -C number
             Like -c but produces a diff with number lines of context.

     -c      Produces a diff with 3 lines of context.  With -c the output for-
             mat is modified slightly: the output begins with identification
             of the files involved and their creation dates and then each
             change is separated by a line with fifteen *'s.  The lines re-
             moved 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 `! '.  Changes which lie within 3
             lines of each other are grouped together on output.

     -D string
             Creates a merged version of file1 and file2 on the standard out-
             put, 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.

     -e      Produces output in a form suitable as input for the editor utili-
             ty, ed(1), which can then be used to convert file1 into file2.

             Extra commands are added to the output when comparing directories
             with -e, so that the result is a sh(1) script for converting text
             files which are common to the two directories from their state in
             dir1 to their state in dir2.

     -f      Identical output to that of the -e flag, but in reverse order.
             It cannot be digested by ed(1).

     -n      Produces a script similar to that of -e, but in the opposite or-
             der and with a count of changed lines on each insert or delete
             command.  This is the form used by rcsdiff(1).

     -q      Just print a line when the files differ.  Does not output a list
             of changes.

     -U number
             Like -u but produces a diff with number lines of context.

     -u      Produces a unified diff with 3 lines of context.  A unified diff
             is similar to the context diff produced by the -c option.  Howev-
             er, unlike with -c, all lines to be changed (added and/or re-
             moved) are present in a single section.

     Comparison options:

     -a      Treat all files as ASCII text.  Normally diff will simply print
             ``Binary files ... differ'' if files contain binary characters.
             Use of this option forces diff to produce a diff.

     -b      Causes trailing blanks (spaces and tabs) to be ignored, and other
             strings of blanks to compare equal.

     -d      Try very hard to produce a diff as small as possible.  This may
             consume a lot of processing power and memory when processing
             large files with many changes.

     -I pattern
             Ignores changes, insertions, and deletions whose lines match the
             extended regular expression pattern.  Multiple -I patterns may be
             specified.  All lines in the change must match some pattern for
             the change to be ignored.  See re_format(7) for more information
             on regular expression patterns.

     -i      Ignores the case of letters.  E.g., ``A'' will compare equal to
             ``a''.

     -L label
             Print label instead of the first (and second, if this option is
             specified twice) file name and time in the context or unified
             diff header.

     -l      Long output format; each text file diff'd is piped through pr(1)
             to paginate it; other differences are remembered and summarized
             after all text file differences are reported.

     -p      With unified and context diffs, show with each change the first
             40 characters of the last line before the context beginning with
             a letter, an underscore or a dollar sign.  For C source code fol-
             lowing standard layout conventions, this will show the prototype
             of the function the change applies to.

     -T      Print a tab rather than a space before the rest of the line for
             the normal, context or unified output formats.  This makes the
             alignment of tabs in the line consistent.

     -t      Will expand tabs in output lines.  Normal or -c output adds char-
             acter(s) to the front of each line which may screw up the inden-
             tation of the original source lines and make the output listing
             difficult to interpret.  This option will preserve the original
             source's indentation.

     -w      Is similar to -b but causes whitespace (blanks and tabs) to be
             totally ignored.  E.g., ``if ( a == b )'' will compare equal to
             ``if(a==b)''.

     Directory comparison options:

     -N      If a file is found in only one directory, act as if it was found
             in the other directory too but was of zero size.

     -P      If a file is found only in dir2, act as if it was found in dir1
             too but was of zero size.

     -r      Causes application of diff recursively to common subdirectories
             encountered.

     -S name
             Re-starts a directory diff in the middle, beginning with file
             name.

     -s      Causes diff to report files which are the same, which are other-
             wise not mentioned.

     -X file
             Exclude files and subdirectories from comparison whose basenames
             match lines in file.  Multiple -X options may be specified.

     -x pattern
             Exclude files and subdirectories from comparison whose basenames
             match pattern.  Patterns are matched using shell-style globbing
             via fnmatch(3).  Multiple -x options may be specified.

     If both arguments are directories, diff sorts the contents of the direc-
     tories by name, and then runs the regular file diff algorithm, producing
     a change list, on text files which are different.  Binary files which
     differ, common subdirectories, and files which appear in only one direc-
     tory are described as such.  In directory mode only regular files and di-
     rectories are compared.  If a non-regular file such as a device special
     file or FIFO is encountered, a diagnostic message is printed.

     If only one of file1 and file2 is a directory, diff is applied to the
     non-directory file and the file contained in the directory file with a
     filename that is the same as the last component of the non-directory
     file.

     If either file1 or file2 is `-', the standard input is used in its place.

   Output Style
     The default (without -e, -c, or -n options) output contains lines of
     these forms, where XX, YY, ZZ, QQ are line numbers respective of file or-
     der.

     XXaYY        At (the end of) line XX of file1, append the contents of
                  line YY of file2 to make them equal.
     XXaYY,ZZ     Same as above, but append the range of lines, YY through ZZ
                  of file2 to line XX of file1.
     XXdYY        At line XX delete the line.  The value YY tells to which
                  line the change would bring file1 in line with file1.
     XX,YYdZZ     Delete the range of lines XX through YY in file1.
     XXcYY        Change the line XX in file1 to the line YY in file2.
     XX,YYcZZ     Replace the range of specified lines with the line ZZ.
     XX,YYcZZ,QQ  Replace the range XX,YY from file1 with the range ZZ,QQ from
                  file2.

     These lines resemble ed(1) subcommands to convert file1 into file2.  The
     line numbers before the action letters pertain to file1; those after per-
     tain to file2.  Thus, by exchanging a for d and reading the line in re-
     verse order, one can also determine how to convert file2 into file1.  As
     in ed(1), identical pairs (where num1 = num2) are abbreviated as a single
     number.

ENVIRONMENT
     TMPDIR  If the environment variable TMPDIR exists, diff will use the di-
             rectory specified by TMPDIR as the temporary directory.

FILES
     /tmp/diff.XXXXXXXX  Temporary file used when comparing a device or the
                         standard input.  Note that the temporary file is un-
                         linked as soon as it is created so it will not show
                         up in a directory listing.

DIAGNOSTICS
     The diff utility exits with one of the following values:

           0       No differences were found.
           1       Differences were found.
           >1      An error occurred.

SEE ALSO
     cmp(1), comm(1), diff3(1), ed(1), pr(1), sdiff(1), fnmatch(3),
     re_format(7)

STANDARDS
     The diff utility is compliant with the IEEE Std 1003.1-2008 (``POSIX'')
     specification.

     The flags [-aDdIiLlNnPpqSsTtwXx] are extensions to that specification.

HISTORY
     A diff command appeared in Version 6 AT&T UNIX.

BUGS
     When comparing directories with the -b, -w or -i options specified, diff
     first compares the files ala cmp(1), and then decides to run the diff al-
     gorithm if they are not equal.  This may cause a small amount of spurious
     output if the files then turn out to be identical because the only dif-
     ferences are insignificant whitespace or case differences.

OpenBSD 4.7                    February 21, 2010                             4
