8.10 Shell Special Symbol cut command 8.11 sort_wc_uniq command 8.12 tee_t

8.10 Shell Special Symbol Cut command

Command: Cut

Used to intercept a field

Syntax: cut-d ' delimited character ' [-CF] n Here's n is the number

-D: followed by delimited characters, separated by single quotation marks

-C: followed by the first few characters

-F: The next section is followed by the number of blocks

[[email protected] ~]# cat/etc/passwd |cut-d ': '-F 1 |head-n5
Root
Bin
Daemon
cd/
Lp
-D followed by the delimiter character, where a colon is used as the split character, and-F 1 is the first paragraph, and the space between-F and 1 is optional.

[Email protected] ~]# HEAD-N2/ETC/PASSWD|CUT-C2
O
I
[Email protected] ~]# HEAD-N2/ETC/PASSWD|CUT-C1
R
B
[Email protected] ~]# head-n2/etc/passwd|cut-c1-10
root:x:0:0
Bin:x:1:1:
[Email protected] ~]# head-n2/etc/passwd|cut-c5-10
: x:0:0
X:1:1:
The-C can be either 1 digits n or an interval n1-n2, or multiple digits n1,n2,n3

[Email protected] ~]# head-n2/etc/passwd|cut-c1,3,10
Ro0
Bn

8.11 Sort_wc_uniq Command

Command: Sort

Sort for sorting

Syntax: sort [-t delimiter] [-KN1,N2] [-NRU] Here's N1 < N2

-T delimiter: function with the-D one meaning of cut

-N: Sorting with pure numbers

-R: Reverse Sort

-U: To repeat

-KN1,N2: Sorted by N1 interval to N2 interval, can only write-kn1, sort N1 field

[Email protected] ~]# head-n5/etc/passwd |sort
Adm:x:3:4:adm:/var/adm:/sbin/nologin
Bin:x:1:1:bin:/bin:/sbin/nologin
Daemon:x:2:2:daemon:/sbin:/sbin/nologin
Lp:x:4:7:lp:/var/spool/lpd:/sbin/nologin
Root:x:0:0:root:/root:/bin/bash
If sort does not have any options, then the first character is backward, then the ASCII values are compared, and finally they are output in ascending order.

[Email protected] ~]# head-n5/etc/passwd |sort-t:-k3-n
Root:x:0:0:root:/root:/bin/bash
Bin:x:1:1:bin:/bin:/sbin/nologin
Daemon:x:2:2:daemon:/sbin:/sbin/nologin
Adm:x:3:4:adm:/var/adm:/sbin/nologin
Lp:x:4:7:lp:/var/spool/lpd:/sbin/nologin
-T followed by a delimiter,-K followed by a number, a string that is sorted on the first range, and-n indicates the use of a purely numeric sort

[Email protected] ~]# head-n5/etc/passwd |sort-t:-k3,5-r
Lp:x:4:7:lp:/var/spool/lpd:/sbin/nologin
Adm:x:3:4:adm:/var/adm:/sbin/nologin
Daemon:x:2:2:daemon:/sbin:/sbin/nologin
Bin:x:1:1:bin:/bin:/sbin/nologin
Root:x:0:0:root:/root:/bin/bash
-k3,5 represents a string sort from 3rd to 5th,-R for reverse ordering

An error occurred because T: there is no space behind it.

Command: WC

The number of rows, characters, and words used to count the document, and the commonly used options are:

-L: Count rows

-M: Statistics of characters

-W: Number of statistical words

[Email protected] ~]# WC/ETC/PASSWD
Panax Notoginseng 1220/etc/passwd
[Email protected] ~]# wc-l/etc/passwd
27/etc/passwd
[Email protected] ~]# wc-m/etc/passwd
1220/etc/passwd
[Email protected] ~]# wc-w/etc/passwd
37/etc/passwd
WC does not follow any options, directly with the document, it will be the number of rows, words, characters in turn output.

Command: Uniq

To repeat the line, the most common option for Amin is only one:

-C: Count the number of repeated rows and write the number of lines in front

[Email protected] ~]# vim Testb.txt
Write the following content into Testb.txt, save.

111
222
111
333
The premise of using Uniq is to sort the files first, otherwise it doesn't work.

[Email protected] ~]# Uniq testb.txt
111
222
111
333
[Email protected] ~]# sort Testb.txt |uniq
111
222
333
[Email protected] ~]# sort Testb.txt |uniq-c
2 111
1 222
1 333

8.12 tee_tr_split Command

Command: Tee

followed by the file name, similar to the redirect ">", but the specific weighting is a feature that is also displayed on the screen while writing the file to the file that follows it.

[Email protected] ~]# echo "AAAAAAAAAAAAAAAAAAAAAAAAAAA" |tee testb.txt
Aaaaaaaaaaaaaaaaaaaaaaaaaaa
[email protected] ~]# cat Testb.txt
Aaaaaaaaaaaaaaaaaaaaaaaaaaa
Tee common Word pipe "|" after.

Command: TR

Substitution characters, commonly used to handle special symbols appearing in a document, such as ^m symbols appearing in a DOS document. There are two common options:

-D: Delete a character, followed by the character you want to delete

-S: Remove repeated characters

The most common is to capitalize the lowercase: tr ' [A-z] ' [A-z] '

[[email protected] ~]# head-n2/etc/passwd |tr ' [A-z] ' [A-z] '
Root:x:0:0:root:/root:/bin/bash
Bin:x:1:1:bin:/bin:/sbin/nologin
Of course, replacing a character is also possible.

[[email protected] ~]# grep ' root '/etc/passwd |tr ' r ' R '
Root:x:0:0:root:/root:/bin/bash
Operator:x:11:0:operator:/root:/sbin/nologin
However, the substitution, deletion and repetition are all aimed at one character and have some limitations. If it's not working for a string, Amin recommends that you simply understand the TR, and you'll learn more about the tools you can implement for string manipulation.

Command: Split

Cutting documents, common options:

-B: Divide the document by size in bytes

[Email protected] ~]# mkdir Split_dir
[Email protected] ~]# CD!$
CD Split_dir
[Email protected] split_dir]# cp/etc/passwd.
[Email protected] split_dir]# split-b500 passwd
[[email protected] split_dir]# ls
passwd XAA Xab Xac
If split does not specify a target file name, it will be Xaa xab ... Such a filename to access the cut file. Of course we can also specify the target file name:

[Email protected] split_dir]# split-b500 passwd 123
[[email protected] split_dir]# ls
123AA 123ab 123ac passwd
-L: Split document by number of rows

8.13 Shell Special Symbol

$ In addition to the identifier used in front of the variable, there is also a magic, that is, and '! ' used together.
[[email protected] ~]# ls testb.txt
Testb.txt
[[email protected] ~]# ls!$
LS Testb.txt
Testb.txt
'!$ ' represents the last variable in the previous hit (in short, the last thing that appears in the previous command) For example, the top command is finally Testb.txt, so entering!$ under the current command represents Testb.txt.

; Semicolon Usually we are in a row to hit a command, and then enter the run, so you want to run two or two more commands in a row? You need to add a ";" between the commands.
[[email protected] ~]# ls-d test; touch test111; ls-d Test
Test test1 test2 test3 Testa Testb.txt
Test test1 test111 test2 test3 Testa Testb.txt
~: User's home directory, if Root is/root, ordinary user is/home/username
[Email protected] ~]# CD ~
[Email protected] ~]# pwd
/root
[email protected] ~]# su test
[Email protected] root]$ CD ~
[Email protected] ~]$ pwd
/home/test

&: If you want to put a command in the background, you need to add this symbol. This is typically used when the command runs for a very long time.
[Email protected] ~]# sleep &
[1] 3260
[[email protected] ~]# jobs
[1]+ Running Sleep &

, >>, 2>, 2>> in front of the directional symbols > and >> the meaning of substitution and append, and then there are two symbols that are here 2> and 2>> respectively for error redirection and error append redirection, When we run a command error, the error message will be output to the current screen, if you want to redirect to a text, you need to use 2> or 2>>
[[email protected] ~]# ls AAAA
LS: Unable to access AAAA: No file or directory
[1]+ Done Sleep 30
[[email protected] ~]# ls AAAA
LS: Unable to access AAAA: No file or directory
[email protected] ~]# ls AAAA 2>/tmp/error
[Email protected] ~]# Cat/tmp/error
LS: Unable to access AAAA: No file or directory
[email protected] ~]# ls AAAA 2>>/tmp/error
[Email protected] ~]# Cat/tmp/error
LS: Unable to access AAAA: No file or directory
LS: Unable to access AAAA: No file or directory
[] in brackets, the middle is a combination of characters, which represents either of the intermediate characters.
[Email protected] ~]# ls-d test*
Test test1 test111 test2 test3 Testa Testb.txt
[Email protected] ~]# ls-d Test[1-3]
Test1 test2 Test3
[Email protected] ~]# ls-d TEST[1A3]
Test1 Test3 Testa
[Email protected] ~]# ls-d test[0-9]
Test1 test2 Test3
[Email protected] ~]# ls-d test[0-9a-z]
Test1 test2 test3 Testa
&& | |
A semicolon has just been mentioned above for the delimiter between multiple commands. There are also two special symbols that can be used in the middle of multiple commands, that is, "&&" and "| |" Below are all listed in the following Amin:

Command1; Command2
Command1 && Command2
Command1 | | Command2
When using ";", Command2 will be executed regardless of whether Command1 is executed successfully;

When using "&&", only if the Command1 is executed successfully, Command2 will execute, otherwise command2 not execute;

When using "| |", the Command1 execution succeeds Command2 not execute, otherwise go to execute Command2, in short Command1 and Command2 always have a command to execute.

Before doing the experiment, Amin want to remove all the test*, but the deletion, but the prompt said that the authority is not enough, the following is the process of eliminating the problem Amin:

[Email protected] ~]# RM-RF test
RM: Unable to delete "Test2/test1": Insufficient permissions
RM: Unable to delete "Test2/test3": Insufficient permissions
RM: Unable to delete "Test2/test4": Insufficient permissions
[[email protected] ~]# ls test
Test1 Test3 test4
[Email protected] ~]# lsattr test
-----a-------E-test2/test1
----I--------E-test2/test3
-------------E-test2/test4
[Email protected] ~]# chattr-a test2/test1
[Email protected] ~]# chattr-i test2/test3
[Email protected] ~]# RM-RF test
RM: Unable to delete "Test2/test1": Insufficient permissions
RM: Unable to delete "Test2/test3": Insufficient permissions
RM: Unable to delete "Test2/test4": Insufficient permissions
[[email protected] ~]# ls test
Test1 Test3 test4
[Email protected] ~]# LS-LD test
Drwxrwxr-x 2 root root 4096 May 10:12 test2
[Email protected] ~]# ls-l test2/
-rw-r--r--1 root root 6 May 10:20 Test2/test1
-rw-r--r--1 root root 0 May 10:11 test2/test3
-rw-r--r--1 root root 0 May 10:12 test2/test4
[Email protected] ~]# lsattr test2/
-------------E-test2/test1
-------------E-test2/test3
-------------E-test2/test4
[Email protected] ~]# lsattr test2
-------------E-test2/test1
-------------E-test2/test3
-------------E-test2/test4
[Email protected] ~]# lsattr-d test2
----I--------E-test2
[Email protected] ~]# chattr-i test2/
[Email protected] ~]# RM-RF test2/
If you have done the same experiment with Amin before, I believe you will have the same problem. Next, Amin to explain the effects of the two special symbols "&&" and "| |" By doing experiments:

[email protected] ~]# Touch test1 test3
[[email protected] ~]# ls test2 && touch test2
LS: Unable to access test2: No file or directory
[[email protected] ~]# ls test2
LS: Unable to access test2: No file or directory
[[email protected] ~]# ls test2 | | Touch Test2
LS: Unable to access test2: No file or directory
[[email protected] ~]# ls test*
Test1 test2 Test3

8.10 Shell Special Symbol cut command 8.11 sort_wc_uniq command 8.12 tee_t