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DESCRIPTION

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.