diff – differential file comparator|
diff [ –abcefmnruw ] file1 ... file2|
Diff tells what lines must be changed in two files to bring them
into agreement. 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 directories are compared by the method of diff for text
cmp(1) otherwise. If more than two file names are given, then
each argument is compared to the last argument as above. The –r
option causes diff to process similarly named subdirectories recursively.
When processing more than one file, diff prefixes file differences
with a single line listing the two differing files, in
the form of a diff command line. The –m flag causes this behavior
even when processing single files. |
The normal output contains lines of these forms:
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 `>'.
The –b option causes trailing blanks (spaces and tabs) to be ignored and other strings of blanks to compare equal. The –w option causes all white–space to be removed from input lines before applying the difference algorithm.
The –n option prefixes each range with file: and inserts a space around the a, c, and d verbs. The –e option produces a script of a, c and d commands for the editor ed, which will recreate file2 from file1. The –f option produces a similar script, not useful with ed, in the opposite order. It may, however, be useful as input to a stream–oriented post–processor.
The –c option includes three lines of context around each change, merging changes whose contexts overlap. In this mode, diff prints – and + instead of < and > because the former are easier to distinguish when mixed. The –a flag displays the entire file as context.
The –u option provides a unix–compatible unified diff. This format
is similar to that provided by –c. However, the + and – prefixes
are not separated from the rest of the line by spaces, and the
file header is in the following format:
cmp(1), comm(1), ed(1), idiff(1)|
Exit status is the empty string for no differences, some for some,
and error for trouble.|
Editing scripts produced under the –e or –f option are naive about
creating lines consisting of a single `.'. |
When running diff on directories, the notion of what is a text
file is open to debate.