4BSD/usr/man/cat1/diff.1
DIFF(1) UNIX Programmer's Manual DIFF(1)
NAME
diff - differential file and directory comparator
SYNOPSIS
diff [ -l ] [ -r ] [ -s ] [ -cefh ] [ -b ] dir1 dir2
diff [ -cefh ] [ -b ] file1 file2
diff [ -D_s_t_r_i_n_g ] [ -b ] file1 file2
DESCRIPTION
If both arguments are directories, _d_i_f_f sorts the contents
of the directories by name, and then runs the regular file
_d_i_f_f algorithm (described below) on text files which are
different. Binary files which differ, common subdirec-
tories, and files which appear in only one directory are
listed. Options when comparing directories are:
-l long output format; each text file _d_i_f_f is piped
through _p_r(1) to paginate it, other differences are
remembered and summarized after all text file differ-
ences are reported.
-r causes application of _d_i_f_f recursively to common sub-
directories encountered.
-s causes _d_i_f_f to report files which are the same, which
are otherwise not mentioned.
-Sname
starts a directory _d_i_f_f in the middle beginning with
file _n_a_m_e.
When run on regular files, and when comparing text files
which differ during directory comparison, _d_i_f_f tells what
lines must be changed in the files to bring them into agree-
ment. Except in rare circumstances, _d_i_f_f finds a smallest
sufficient set of file differences. If neither _f_i_l_e_1 nor
_f_i_l_e_2 is a directory, then either may be given as `-', in
which case the standard input is used. If _f_i_l_e_1 is a direc-
tory, then a file in that directory whose file-name is the
same as the file-name of _f_i_l_e_2 is used (and vice versa).
There are several options for output format; the default
output format contains lines of these forms:
_n_1 a _n_3,_n_4
_n_1,_n_2 d _n_3
_n_1,_n_2 c _n_3,_n_4
These lines resemble _e_d commands to convert _f_i_l_e_1 into
_f_i_l_e_2. The numbers after the letters pertain to _f_i_l_e_2. In
fact, by exchanging `a' for `d' and reading backward one may
ascertain equally how to convert _f_i_l_e_2 into _f_i_l_e_1. As in
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DIFF(1) UNIX Programmer's Manual DIFF(1)
_e_d, identical pairs where _n_1 = _n_2 or _n_3 = _n_4 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 `>'.
Except for -b, which may be given with any of the others,
the following options are mutually exclusive:
-e producing a script of _a, _c and _d commands for the
editor _e_d, which will recreate _f_i_l_e_2 from _f_i_l_e_1.
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 _e_d scripts ($2,$3,...) made by
_d_i_f_f 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 compar-
ing directories with -e, so that the result is a
_s_h(1) script for converting text files which are
common to the two directories from their state in
_d_i_r_1 to their state in _d_i_r_2.
-f produces a script similar to that of -e, not useful
with _e_d, and in the opposite order.
-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
_f_i_l_e_1 are marked with `-'; those added to _f_i_l_e_2 are
marked `+'. Lines which are changed from one file
to the other are marked in both files with `!'.
-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.
-Dstring causes _d_i_f_f to create a merged version of _f_i_l_e_1 and
_f_i_l_e_2 on the standard output, with C preprocessor
controls included so that a compilation of the
result without defining _s_t_r_i_n_g is equivalent to
compiling _f_i_l_e_1, while defining _s_t_r_i_n_g will yield
_f_i_l_e_2.
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DIFF(1) UNIX Programmer's Manual DIFF(1)
-b causes trailing blanks (spaces and tabs) to be
ignored, and other strings of blanks to compare
equal.
FILES
/tmp/d?????
/usr/lib/diffh for -h
/usr/bin/pr
SEE ALSO
cmp(1), cc(1), comm(1), ed(1)
DIAGNOSTICS
Exit status is 0 for no differences, 1 for some, 2 for trou-
ble.
BUGS
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,
_d_i_f_f first compares the files ala _c_m_p, and then decides to
run the _d_i_f_f algorithm 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 differences are
insignificant blank string differences.
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