DIFF(1) BSD General Commands Manual DIFF(1)

NAME

diff — differential file and directory comparator

SYNOPSIS

diff [-cefhn] [-biwt] file1 file2
diff [-Dstring] [-biw] file1 file2
diff [-l] [-r] [-s] [-cefhn] [-biwt] [-Sname] dir1 dir2

DESCRIPTION

The diff utility compares the contents of file1 and file2 and writes to the standard output the list of changes necessary to convert one file into the other. No output is produced if the files are identical.

Output options (mutually exclusive):

-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 previous ’’diff -c’’ but the resulting output is usually much easier to interpret.)

-e

produces output in a form suitable as input for the editor utility, ed(1), which can then be used to convert file1 into file2.

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

identical output to that of the -e flag, but in reverse order. It cannot be digested by ed(1).

-h

Invokes an alternate algorithm which can handle files of very long lengths. There is a trade off. The algorithm can only deal with changes which are clearly delimited and brief. Long sections of changes and overlaps will confuse it.

-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 rcsdiff(1).

-Dstring

creates 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.

Comparison options:

-b

causes trailing blanks (spaces and tabs) to be ignored, and other strings of blanks to compare equal.

-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 screw 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.

-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)’’.

Directory comparison options:

-l

long output format; each text file diff´d 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 diff recursively to common subdirectories encountered.

-s

causes diff to report files which are the same, which are otherwise not mentioned.

-Sname

re-starts a directory diff in the middle beginning with file name.

If both arguments are directories, diff sorts the contents of the directories by name, and then runs the regular file diff algorithm, producing a change list, on text files which are different. Binary files which differ, common subdirectories, and files which appear in only one directory are described as such.

If only one of file1 and file2 is a directory, diff is applied to the non-directory file and the file contained in the directory file with a filename that is the same as the last component of the non-directory file.

If either file1 or file2 is ’-’, the standard input is used in its place.

Output Style
The default (without -e, -c, or -n options) output contains lines of these forms, where XX, YY, ZZ, QQ are line numbers respective of file order.

XXaYY

At (the end of) line XX of file1, append the contents of line YY of file2 to make them equal.

XXaYY,ZZ

Same as above, but append the range of lines, YY through ZZ of file2 to line XX of file1.

XXdYY

At line XX delete the line. The value YY tells to which line the change would bring file1 in line with file1.

XX,YYdZZ

Delete the range of lines XX through YY in file1.

XXcYY

Change the line XX in file1 to the line YY in file2.

XX,YYcZZ

Replace the range of specified lines with the line ZZ.

XX,YYcZZ,QQ

Replace the range XX,YY from file1 with the range ZZ,QQ from file2.

These lines resemble ed(1) subcommands to convert file1 into file2. The line numbers before the action letters pertain to file1; those after pertain to file2. Thus, by exchanging a for d and reading the line in reverse order, one can also determine how to convert file2 into file1. As in ed(1), identical pairs (where num1 = num2) are abbreviated as a single number.

ENVIRONMENT
TMPDIR

If the environment variable TMPDIR exists, diff will use the directory specified by TMPDIR as the temporary directory.

FILES
/tmp/d?????
/usr/bin/diffh

Alternate algorithm version (used by option -h).

/usr/bin/diff

for directory diffs

/usr/bin/pr

used by the -l option.

SEE ALSO

cmp(1), cc(1), comm(1), ed(1), diff3(1)

DIAGNOSTICS

The diff utility exits with one of the following values:

0

No differences were found.

1

Differences were found.

>1

An error occurred.

BUGS

The -f and -e options do not provide special handling for lines on which the first and only character is “.”. This can cause problems for ed(1).

When comparing directories with the -b, -w or -i options specified, diff first compares the files ala cmp, and then decides to run the diff 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 white space or case differences.

HISTORY

A diff command appeared in Version 6 AT&T UNIX.

4th Berkeley Distribution June 30, 1993 4th Berkeley Distribution