linux Commands: diff command

1. Command format:

diff[parameter [file 1 or directory 1][file 2 or directory 2]

2. Command function:

The diff command can compare individual files or directory contents. If you specify that the comparison is a file, it is only valid if the input is a text file. Compare the similarities and differences of text files in a row-by-line manner. If you specify a table of contents, the diff command compares a text file with the same name in two directories. Lists the different binaries, common subdirectories, and files that appear only in one directory.

3. Command parameters:

-Specify how many lines of text to display. This parameter must be used in conjunction with the-C or-u parameter.

The-A or--text diff preset will only compare text files line by row.

-B or--ignore-space-change do not check for differences in whitespace characters.

-B or--ignore-blank-lines does not check for blank lines.

-C Displays all the text and marks the difference.

-C or--context is the same as executing the "-c-" directive.

-D or--minimal use different algorithms to compare in smaller units.

-D or ifdef the output format of this parameter is available for the predecessor Processor macro.

-E or--ed the output format of this parameter is available for the ed script file.

The-f or-forward-ed output is formatted like an ED script file, but is displayed differently in the order of the original files.

-h or--speed-large-files can speed up when comparing large files.

-L or--ignore-matching-lines if two files are different in a few lines, and these lines both contain the characters or strings specified in the option, the differences between the two files are not displayed.

-I or--ignore-case do not check for differences in case.

-L or--paginate the results to the PR program for paging.

-N or--rcs displays the comparison results in RCS format.

-N or--new-file when comparing directories, if file a only appears in a directory, the preset will display: Only in directory: file A If you use the-n parameter, diff will compare file A with a blank file.

-P If the file is compared to a C language code file, the name of the function where the difference is displayed.

-P or--unidirectional-new-file is similar to-N, but this file is compared to a blank file only if the second directory contains a file that is not in the first directory.

-Q or--brief display only if there is no difference, no detailed information is displayed.

-R or--recursive to compare files in subdirectories.

-S or--report-identical-files if no differences are found, the message is still displayed.

-S or--starting-file when comparing directories, start comparing from the specified file.

-T or--expand-tabs expands the tab character when it is output.

-T or--initial-tab the tab character before each line to align.

-u,-u or--unified= displays the different contents of the file in a merged manner.

-V or--version displays version information.

-W or--ignore-all-space ignores all whitespace characters.

-W or--width specifies the column width when using the-y parameter.

-X or--exclude does not compare the files or directories specified in the options.

-X or--exclude-from you can save the file or directory type as a text file, and then specify the text file in =.

-Y or--side-by-side displays the similarities and differences of the files in a parallel manner.

--help display Help.

--left-column when using the-y parameter, if the contents of one row of two files are the same, the contents of that row are displayed only in the field on the left.

--suppress-common-lines displays only the differences when using the-y parameter.

4. Usage examples:

Example 1: Comparison of two files

Command:

Output:

[Email protected] test3]# diff Log2014.log Log2013.log

3c3

< 2014-03

---

> 2013-03

8c8

< 2013-07

---

> 2013-08

11,12d10

< 2013-11

< 2013-12

Description

The "3c3" and "8c8" above indicate that Log2014.log and Log20143log files differ in rows 3 and 8th, and "11,12D10" means that the first file is 11th and 12 rows longer than the second file.

The normal display format for diff has three tips:

A-add

C-change

D-delete

Example 2: Side-by format output

Command:

Diff Log2013.log Log2014.log-y-W 50

Output:

[[Email protected] test3]# diff Log2014.log Log2013.log-y-W 50

2013-01 2013-01

2013-02 2013-02

2014-03 | 2013-03

2013-04 2013-04

2013-05 2013-05

2013-06 2013-06

2013-07 2013-07

2013-07 | 2013-08

2013-09 2013-09

2013-10 2013-10

2013-11 <

2013-12 <

[[Email protected] test3]# diff Log2013.log Log2014.log-y-W 50

2013-01 2013-01

2013-02 2013-02

2013-03 | 2014-03

2013-04 2013-04

2013-05 2013-05

2013-06 2013-06

2013-07 2013-07

2013-08 | 2013-07

2013-09 2013-09

2013-10 2013-10

> 2013-11

> 2013-12

Description

| Indicates that the contents of the front and back 2 files are different

"<" indicates that the following file is 1 lines less than the previous file

">" indicates that the following file has 1 lines more than the previous file

Example 3: Context output format

Command:

Diff Log2013.log Log2014.log-c

Output:

[Email protected] test3]# diff Log2013.log Log2014.log-c

Log2013.log 2012-12-07 16:36:26.000000000 +0800

---log2014.log 2012-12-07 18:01:54.000000000 +0800

***************

1,10 * * *

2013-01

2013-02

! 2013-03

2013-04

2013-05

2013-06

2013-07

! 2013-08

2013-09

2013-10

---1,12----

2013-01

2013-02

! 2014-03

2013-04

2013-05

2013-06

2013-07

! 2013-07

2013-09

2013-10

+ 2013-11

+ 2013-12[[email protected] test3]# diff Log2014.log Log2013.log-c

Log2014.log 2012-12-07 18:01:54.000000000 +0800

---log2013.log 2012-12-07 16:36:26.000000000 +0800

***************

1,12 * * *

2013-01

2013-02

! 2014-03

2013-04

2013-05

2013-06

2013-07

! 2013-07

2013-09

2013-10

-2013-11

-2013-12

---1,10----

2013-01

2013-02

! 2013-03

2013-04

2013-05

2013-06

2013-07

! 2013-08

2013-09

2013-10[[email protected] test3]#

Description

In this way, a description of the comparison file is made in the first two lines, here are three special characters:

The "+" comparison of the latter of the files is more than the previous line

"-" compares the latter of the file with a smaller line than the previous

“！ "Compare files with two different lines

Example 4: Unified format output

Command:

Diff Log2014.log Log2013.log-u

Output:

[Email protected] test3]# diff Log2014.log Log2013.log-u

---log2014.log 2012-12-07 18:01:54.000000000 +0800

+ + + log2013.log 2012-12-07 16:36:26.000000000 +0800

@@ -1,12 +1,10 @@

2013-01

2013-02

-2014-03

+2013-03

2013-04

2013-05

2013-06

2013-07

-2013-07

+2013-08

2013-09

2013-10

-2013-11

-2013-12

Description

The first part of it is also the basic information of the file:

---log2014.log 2012-12-07 18:01:54.000000000 +0800

+ + + log2013.log 2012-12-07 16:36:26.000000000 +0800

"---" means the document before the change, and "+ + +" means the document after the change.

The second part, the position of the change with two @ as the first and end.

@@ -1,12 +1,10 @@

The preceding " -1,12" is divided into three parts: the minus sign indicates the first file (that is, Log2014.log), "1" means line 1th, and "12" means 12 rows in a row. Together, it means that the following is the first file, starting from line 1th, 12 consecutive lines. Similarly, "+1,10" means that after a change, the second file becomes a row of 10 lines starting from line 1th.

Example 5: Compare folders differently

Command:

Diff Test3 Test6

Output:

[Email protected] test]# diff test3 Test6

Only in Test6:linklog.log

Only in Test6:log2012.log

Diff Test3/log2013.log Test6/log2013.log

1,10c1,3

< 2013-01

< 2013-02

< 2013-03

< 2013-04

< 2013-05

< 2013-06

< 2013-07

< 2013-08

< 2013-09

< 2013-10

---

> hostnamebaidu=baidu.com

> hostnamesina=sina.com

> Hostnames=true

Diff Test3/log2014.log Test6/log2014.log

1,12d0

< 2013-01

< 2013-02

< 2014-03

< 2013-04

< 2013-05

< 2013-06

< 2013-07

< 2013-07

< 2013-09

< 2013-10

< 2013-11

< 2013-12

Only in Test6:log2015.log

Only in Test6:log2016.log

Only in Test6:log2017.log

[Email protected] test]#

Description

Example 6: Compare two different files and produce patches

Command:

Diff-run Log2013.log Log2014.log >patch.log

Output:

[Email protected] test3]# diff-run log2013.log log2014.log >patch.log

[email protected] test3]# LL

Total 12

-rw-r--r--2 root root 12-07 16:36 Log2013.log

-rw-r--r--1 root root 12-07 18:01 Log2014.log

-rw-r--r--1 root root 248 12-07 21:33 Patch.log

[email protected] test3]# cat Patc.log

Cat:patc.log: No file or directory

[email protected] test3]# cat Patch.log

---log2013.log 2012-12-07 16:36:26.000000000 +0800

+ + + log2014.log 2012-12-07 18:01:54.000000000 +0800

@@ -1,10 +1,12 @@

2013-01

2013-02

-2013-03

+2014-03

2013-04

2013-05

2013-06

2013-07

-2013-08

+2013-07

2013-09

2013-10

+2013-11

+2013-12[[email protected] test3]#

Description

Example 7: Patching

Command:

Output:

[email protected] test3]# cat Log2013.log

2013-01

2013-02

2013-03

2013-04

2013-05

2013-06

2013-07

2013-08

2013-09

2013-10[[email protected] test3]# patch Log2013.log Patch.log

Patching file Log2013.log

[Email protected] test3]#

[email protected] test3]# cat Log2013.log

2013-01

2013-02

2014-03

2013-04

2013-05

2013-06

2013-07

2013-07

2013-09

2013-10

2013-11

Linux commands: diff command