ODIFF(1)ODIFF(1)NAMEodiff - differential file and directory comparator
SYNOPSISodiff [-lrs] [-Sname] [-cefhn] [-xpat] [-biwt] dir1 dir2
odiff [-cefhn] [-biwt] file1 file2
odiff [-Dstring] [-biw] file1 file2
DESCRIPTION
This used to be the diff command. The current diff command is a port of
GNU diff, and is upward compatible with this odiff.
If both arguments are directories, odiff sorts the contents of the
directories by name, and then runs the regular file odiff algorithm
(described below) on text files which are different. Binary files which
differ, common subdirectories, and files which appear in only one
directory are listed. Options when comparing directories are:
-l long output format; each text file odiff is piped through pr(1) to
paginate it, other differences are remembered and summarized after
all text file differences are reported.
-r causes application of odiff recursively to common subdirectories
encountered.
-s causes odiff to report files which are the same, which are otherwise
not mentioned.
-Sname
starts a directory odiff in the middle beginning with file name.
-xpat
adds pat to a list of regular expressions. There can be several
-xpat options. Any directory or file name matching one of the
patterns is skipped. The special characters available in the
pattern are defined in regcmp(3X), and are similar to those used in
ed and sed. For example, the following command will ignore all
"hidden" files and all RCS archives:
odiff-r '-x^\.' '-x,v$' foo bar
When run on regular files, and when comparing text files which differ
during directory comparison, odiff tells what lines must be changed in
the files to bring them into agreement. Except in rare circumstances,
odiff finds a smallest sufficient set of file differences. If neither
file1 nor file2 is a directory, then either may be given as `-', in which
case the standard input is used. If file1 is a directory, then a file in
that directory whose file-name is the same as the file-name of file2 is
used (and vice versa). If both file1 and file2 are directories, then
files (or files and directories with -r) with identical names are
compared.
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There are several options for output format; the default output format
contains lines of these forms:
n1 a n3,n4
n1,n2 d n3
n1,n2 c n3,n4
These lines resemble ed commands to convert file1 into file2. The
numbers after the letters pertain to file2. In fact, by exchanging `a'
for `d' and reading backward one may ascertain equally how to convert
file2 into file1. As in ed, identical pairs where n1 = n2 or n3 = n4 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 ed,
which will recreate file2 from file1. 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 ed scripts ($2,$3,...) made by odiff 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 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 produces a script similar to that of -e, not useful with ed, 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 the RCS commands for storing
a revision change.
-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 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 <context> lines of each other
are grouped together on output. (This is a change from the
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previous ``diff -c'' but the resulting output is usually much
easier to interpret.)
-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 odiff to create a merged version of file1 and file2 on
the standard output, 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.
-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 compare 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 foul up the
indentation of the original source lines and make the output
listing difficult to interpret. This option will preserve the
original source's indentation.
FILES
/usr/bin/odiff executable for odiff. /bin/diff executable for
GNU derived diff.
/usr/lib/diffh executable used for the -h option.
/tmp/d????? working files.
/bin/pr executed by the -l option.
SEE ALSObdiff(1), cc(1), cmp(1), comm(1), diff(1), diff3(1), ed(1), regcmp(3X)DIAGNOSTICS
Exit status is 0 for no differences, 1 for some differences, 2 for
trouble.
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, odiff
first compares the files a la cmp(1), and then decides to run the odiff
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 or case differences.
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ODIFF(1)ODIFF(1)PERFORMANCE
The GNU derived diff and older BSD derived odiff use different
algorithms. If the two files to be compared fit in main memory, then
diff is faster, but if they don't fit, diff can cause severe paging. The
odiff algorithm uses a small, fixed amount of memory even on large files.
The multiple pass algorithm of odiff is up to two or three times slower
than diff, on files that fit in memory, but can be many times faster on
files that don't fit.
The diff command automatically invokes the odiff (searching for odiff
along $PATH) on files that have a combined size larger than one-fourth of
memory size, if no GNU specific diff options were specified. If that
fails, then diff attempts the work itself.
You can force either variant: specifying -H always gets diff, specifying
odiff always gets odiff.
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