The format for running the
diff command is:
diff options... files...
In the simplest case, two file names from-file and
to-file are given, and
diff compares the contents of
from-file and to-file. A file name of
- stands for
text read from the standard input. As a special case,
diff - -
compares a copy of standard input to itself.
If one file is a directory and the other is not,
the file in the directory whose name is that of the non-directory.
The non-directory file must not be
If two file names are given and both are directories,
diff compares corresponding files in both directories, in
alphabetical order; this comparison is not recursive unless the
--recursive option is given.
compares the actual contents of a directory as if it were a file. The
file that is fully specified may not be standard input, because standard
input is nameless and the notion of "file with the same name" does not
--from-file=file option is given, the number of
file names is arbitrary, and file is compared to each named file.
Similarly, if the
--to-file=file option is given, each
named file is compared to file.
diff options begin with
-, so normally file names
may not begin with
-- as an
argument by itself treats the remaining arguments as file names even if
they begin with
An exit status of 0 means no differences were found, 1 means some
differences were found, and 2 means trouble.