shell special symbols cut, sort_wc_uniq, tee_tr_split, shell special symbols

special symbols

• * any character

• ? any character

• comment character

  Indicates that this command does not take effect, to explain

• \ escape character

[root@localhost ~]# a=1
[root@localhost ~]# b=2
[root@localhost ~]# c=$a$b
[root@localhost ~]# echo $c
12
[root@localhost ~]# c=\$a\$b
[root@localhost ~]# echo $c
$a$b
[root@localhost ~]# 

• | Pipe character, several commands related to pipes

  • cut command: intercept string

cat /etc/passwd |cut -d ":" -f 1,2

-d delimiter

-f specifies the segment number

-c specifies the number of characters, you can't use -d and -f when using it.

 [root@localhost ~]# cat /etc/passwd | head
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
sync:x:5:0:sync:/sbin:/bin/sync
shutdown:x:6:0:shutdown:/sbin:/sbin/shutdown
halt:x:7:0:halt:/sbin:/sbin/halt
mail:x:8:12:mail:/var/spool/mail:/sbin/nologin
operator:x:11:0:operator:/root:/sbin/nologin
[root@localhost ~]# cat /etc/passwd |cut -d ":" -f 1,2
root:x
bin:x
daemon:x
adm:x
lp:x
sync:x
shutdown:x
halt:x
mail:x
operator:x
games:x
ftp:x
nobody:x
systemd-bus-proxy:x
systemd-network:x
dbus:x
polkitd:x
tss:x
postfix:x
sshd:x
chrony:x
user1:x
user2:x
user3:x
[root@localhost ~]# 

• sort : sort command, the default is in Asma order

[root@localhost ~]# sort 1.txt 
>
.
@
《
111n
1.txt
*2
222333
222444
222555
222aaaa
2.txt
333333
4444444
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
halt:x:7:0:halt:/sbin:/sbin/halt
lp:x:4:7:lp:/var/spool/lpd:/sbin/nologin
ls: 无法访问asffsfs.txt: 没有那个文件或目录
mail:x:8:12:mail:/var/spool/mail:/sbin/nologin
operator:x:11:0:operator:/root:/sbin/nologi
root:x:0:0:root:/root:/bin/bash
shutdown:x:6:0:shutdown:/sbin:/sbin/shutdown
sync:x:5:0:sync:/sbin:/bin/sync
[root@localhost ~]# 

-n sort by number, default letters and special symbols will be considered as 0

[root@localhost ~]# sort -n 1.txt 
>
.
@
《
*2
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
halt:x:7:0:halt:/sbin:/sbin/halt
lp:x:4:7:lp:/var/spool/lpd:/sbin/nologin
ls: 无法访问asffsfs.txt: 没有那个文件或目录
mail:x:8:12:mail:/var/spool/mail:/sbin/nologin
operator:x:11:0:operator:/root:/sbin/nologi
root:x:0:0:root:/root:/bin/bash
shutdown:x:6:0:shutdown:/sbin:/sbin/shutdown
sync:x:5:0:sync:/sbin:/bin/sync
1.txt
2.txt
111n
222aaaa
222333
222444
222555
333333
4444444
[root@localhost ~]# 

-r reverse order, reverse to Asma

[root@localhost ~]# sort -r 1.txt 
sync:x:5:0:sync:/sbin:/bin/sync
shutdown:x:6:0:shutdown:/sbin:/sbin/shutdown
root:x:0:0:root:/root:/bin/bash
operator:x:11:0:operator:/root:/sbin/nologi
mail:x:8:12:mail:/var/spool/mail:/sbin/nologin
ls: 无法访问asffsfs.txt: 没有那个文件或目录
lp:x:4:7:lp:/var/spool/lpd:/sbin/nologin
halt:x:7:0:halt:/sbin:/sbin/halt
daemon:x:2:2:daemon:/sbin:/sbin/nologin
bin:x:1:1:bin:/bin:/sbin/nologin
adm:x:3:4:adm:/var/adm:/sbin/nologin
4444444
333333
2.txt
222aaaa
222555
222444
222333
*2
1.txt
111n
《
@
.
>
[root@localhost ~]# 

-t Delimiter. -kn1/-kn1,n2

• wc -l : count lines command

[root@localhost ~]# wc -l 1.txt 
25 1.txt

wc -m : count the number of characters

[root@localhost ~]# wc -m 1.txt 
487 1.txt

wc -w : statistical words, separated by blank characters

[root@localhost ~]# wc -w 1.txt 
27 1.txt
[root@localhost ~]# 

• uniq deduplication requires adjacent duplicate words to be removed, so generally sort first and then remove duplicates sort 2.txt |uniq -c

  -c count duplicate lines

tee is similar to >

Visual redirection

[root@localhost ~]# sort 1.txt > a.txt

[root@localhost ~]# cat a.txt 
>
.
@
《
111n
1.txt
*2
222333
222444
222555
222aaaa
2.txt
333333
4444444
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
halt:x:7:0:halt:/sbin:/sbin/halt
lp:x:4:7:lp:/var/spool/lpd:/sbin/nologin
ls: 无法访问asffsfs.txt: 没有那个文件或目录
mail:x:8:12:mail:/var/spool/mail:/sbin/nologin
operator:x:11:0:operator:/root:/sbin/nologi
root:x:0:0:root:/root:/bin/bash
shutdown:x:6:0:shutdown:/sbin:/sbin/shutdown
sync:x:5:0:sync:/sbin:/bin/sync

[root@localhost ~]# sort 1.txt |tee  a.txt
>
.
@
《
111n
1.txt
*2
222333
222444
222555
222aaaa
2.txt
333333
4444444
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
halt:x:7:0:halt:/sbin:/sbin/halt
lp:x:4:7:lp:/var/spool/lpd:/sbin/nologin
ls: 无法访问asffsfs.txt: 没有那个文件或目录
mail:x:8:12:mail:/var/spool/mail:/sbin/nologin
operator:x:11:0:operator:/root:/sbin/nologi
root:x:0:0:root:/root:/bin/bash
shutdown:x:6:0:shutdown:/sbin:/sbin/shutdown
sync:x:5:0:sync:/sbin:/bin/sync
[root@localhost ~]# 

• |tee -a Visual append redirection

• tr replace character

[root@localhost ~]# echo "aminglinux" |tr 'a' 'A'
Aminglinux

[root@localhost ~]# echo "aminglinux" |tr '[anx]' '[ANX]'
AmiNgliNuX

[root@localhost ~]# echo "aminglinux" |tr '[a-z]' '[A-Z]'
AMINGLINUX

split

• -b specifies the split size: split -b 100M bigfile filename (the default display is bytes if the unit is not written)

• -l specifies the number of lines to split the file: split -l 1000 bigfile filename

shell special symbols

• $variable prefix, !$ combination, which means the end of the line

• ; Write multiple commands on one line, separated by semicolons

• ~ User home directory, followed by a regular expression that represents a match

• & put it after the command, it will drop the command to the background

• > >> 2> 2>> &>

• [] specifies one of the characters

• || and &&, used between commands

  • || Or means
  • &&
• ||

  If the command prompt before || is successful, the command after || will not be executed, and if the previous command is unsuccessful, the command after || will be executed.

[root@localhost ~]# ls 1a.txt ; wc -l 1.txt
ls: 无法访问1a.txt: 没有那个文件或目录
25 1.txt
[root@localhost ~]# ls 1a.txt || wc -l 1.txt
ls: 无法访问1a.txt: 没有那个文件或目录
25 1.txt
[root@localhost ~]# ls 1.txt || wc -l 1.txt
1.txt
[root@localhost ~]# 

• &&

  If the previous command is executed successfully, the following command will be executed. If the previous command is wrong, the latter command will not be executed.

[root@localhost ~]# ls 1.txt && wc -l 1.txt
1.txt
25 1.txt
[root@localhost ~]# ls 1a.txt && wc -l 1.txt
ls: 无法访问1a.txt: 没有那个文件或目录
[root@localhost ~]#