4.3BSD-UWisc/man/cat1/diff.1
DIFF(1) UNIX Programmer's Manual DIFF(1)
NAME
diff - differential file and directory comparator
SYNOPSIS
diff [ -l ] [ -r ] [ -s ] [ -cefhn ] [ -biwt ] dir1 dir2
diff [ -cefhn ] [ -biwt ] file1 file2
diff [ -D_s_t_r_i_n_g ] [ -biw ] 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, -w, -i or -t which may be given with any of
the others, the following options are mutually exclusive:
-e produces 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.
-n produces a script similar to that of -e, but in the
opposite order and with a count of changed lines on
each insert or delete command. This is the form
used by _r_c_s_d_i_f_f(1).
-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
with `! '.
Changes which lie within <context> lines of each
other are grouped together on output. (This is a
change from the previous ``diff -c'' but the
resulting output is usually much easier to inter-
pret.)
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-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.
-b causes trailing blanks (spaces and tabs) to be
ignored, and other strings of blanks to compare
equal.
-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)''.
-i ignores the case of letters. E.g., ``A'' will com-
pare equal to ``a''.
-t will expand tabs in output lines. Normal or -c
output adds character(s) to the front of each line
which may screw up the indentation of the original
source lines and make the output listing difficult
to interpret. This option will preserve the origi-
nal source's indentation.
FILES
/tmp/d?????
/usr/lib/diffh for -h
/bin/diff for directory diffs
/bin/pr
SEE ALSO
cmp(1), cc(1), comm(1), ed(1), diff3(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, -w or -i options
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
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differences are insignificant blank string or case differ-
ences.
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