diff

Side-by-side file comparison report style

The default file-comparison report begins with a file summary, which lists all the input files and their assignments as file 1, file 2, and so on. If no differences are detected among the files, this listing is replaced by the message Files are identical.

The remainder of the report is a series of pairwise differences, each of which is preceded by a descriptive header line:

******************************** (file summary)
<<< file 1: util.c@@/main/1
>>> file 2: util.c@@/main/3
********************************
----------[after 15]------|-------[inserted 16]------ (header)
                          | char *s;        (difference)
                                                    |-
---------[changed 18]-----|----[changed to 19-21]---- (header)
return ctime(&clock);     | s = ctime(&clock); (difference)
                       -  | s[ strlen(s)-1 ] = '\0';
                          | return s;
                          |-

The –quiet and –diff_format options suppress the file summary. The –headers_only option suppresses the differences, listing the header lines only.

Header lines. Each header line indicates which text lines in the input files were changed and how they were changed. The words describe the change in terms of how the first file was changed to produce the second file. Header lines can have the following formats, where each of A, B, and so on may be a single line number (for example, 46) or a range (for example, 256–290):

----------[after A]----------|--------[inserted B]---------

Insertion of one or more lines. B indicates where the inserted lines occur in the second file. A indicates the corresponding point in the first file.

---------[deleted C]---------|---------[after D]----------

Deletion of one or more lines. C indicates which lines from the first file were deleted. D indicates the corresponding point in the second file.

--------[deleted/moved C]-----|--------[after D now B]--------

Deletion of one or more lines from the first file, to which there corresponds an insertion of the same lines in the second file. Typically, this indicates that a range of lines was moved from one location to another; see inserted/moved below. C indicates where the lines were deleted from the first file; B indicates where these same lines were inserted in the second file. D indicates the point in the second file that corresponds to C.

---------[changed X]----------|----------[changed to Y]---------

One or more lines changed in place. X indicates which lines in the first file were changed. Y indicates where the replacement lines occur in the second file.

--------[after A was C]--------|--------[inserted/moved B]------

Insertion of one or more lines in the second file, to which there corresponds a deletion of the same lines from the second file. Typically, this indicates that a range of lines was moved from one location to another; see deleted/moved above. B indicates where the lines were inserted in the second file; C indicates where these same lines were deleted from the first file; A indicates the point in the first file that corresponds to B.

Differences. diff can report a difference in several ways. When comparing files, its default behavior is to list corresponding lines side by side, and possibly truncated.

A plus sign (+) at the end of a difference line indicates that it has been truncated in the report. To see more of such lines, you can increase the report widthby using the –columns option (or on UNIX and Linux, by using the –tiny option). The minus signs (–) along the vertical separator line indicate the endpoints of the groups of differing lines. They help to distinguish empty lines in the input files from blank space in command output.

Other file comparison report styles

The –serial_format option causes the differences to be reported as entire lines, in above-and-below format instead of side-by-side format. For example:

-----[after 15 inserted 16]-----
>     char *s;
-----[18 changed to 19-21]-----
<     return ctime(&clock);
---
>   s = ctime(&clock);
>   s[ strlen(s)-1 ] = ' ';
>     return s;

The –diff_format option causes both the headers and differences to be reported in the style of the UNIX and Linuxdiff utility, writing a list of the changes necessary to convert the first file being compared into the second file, as follows:

• The first number (or range of numbers in the form n,n) indicates line numbers in the first file being compared.
• The second value is one of the following: a d c. These indicate whether lines are to be added, deleted, or changed.
• The second number (or range of numbers) indicates line numbers in the second file being compared.

When diff compares multiple files, it adds file-identification annotations to the diff-style headers.

The –graphical option displays differences graphically.

Kinds of directory entries

A version of a VOB directory can contain several types of entries:

• File elements. Reported by diff as the element's name (in this directory version), the element's creation time, and the user name of the element's creator. For example:

  obj2 2007-08-12T14:00 akp

  Note: Multiple VOB hard links to the same element will have the same creator and creation time, but different names.
• Directory elements. Reported by diff in the same way as file elements, except that a slash (UNIX and Linux) or backslash (Windows) is appended to the element name. For example:

  sub6/ 2007-08-13T15:00 akp

• VOB symbolic links. Reported by diff as the link's name (in this directory version), followed by – and the text (contents) of the link; the link's creation time; and the user name of the element's creator. For example:

  doctn -> ..\vob1\doctn 2007-08-13T08:44 akp

How differences are reported

The diff report is a series of differences, each of which focuses on one directory entry. A difference can be a simple addition or deletion; it can also involve the renaming of an existing object or the reuse of an existing name for another object. The following examples illustrate the various possibilities.

------------------------------ |---------------[ added ]-------------
                             - | obj2 2007-08-12T14:00 akp

An object named obj2 was added (mkelem, mkdir, or ln) in the second version of the directory.

---------------[ removed ]---------- | ---------------------------
obj5 2007-08-12T14:00 akp                |-

An object named obj5 was removed (rmname) in the second version of the directory.

---------------[ renamed ]------------ |--------[ renamed to ]-------
obj3 2007-08-12T14:00 akp                  | obj3.new 2007-08-12T14:00 akp

An object named obj3 was renamed (mv) to obj3.new in the second version of the directory.

-------------[ old object ]------------ |--------[ new object ]-------
obj4 2007-08-12T14:04 akp                   | obj4 2007-10-19T17:10 akp

In the second version of the directory, an object named obj4 was removed (rmname) and another object was created with that same name.

----------[ old link text ]---------|------[ new link text ]----
doc -> ../vob1/doc 2007-08-13T08:44 akp | doc -> ../vb/doc 2007-09-19T21:01 akp

(Special case of the preceding example) In the second version of the directory, a VOB symbolic link named doc was removed (rmname) and another VOB symbolic link was created with that same name.

---------------[ renamed ]------------|---[ renamed to ]------------
obj4 2007-08-12T14:01 akp                 | obj1 2007-08-12T14:01 akp
---------------[ removed ]------------|-----------------------------
obj1 2007-08-12T14:00 akp                 |-

These two differences show that in the second version of the directory, an object named obj1 was removed and another object was renamed from obj4 to obj1.