Extension:
1. The difference between source exec http://alsww.blog.51cto.com/2001924/1113112
2. A complete collection of Linux special symbols http://ask.apelearn.com/question/7720
3. Sort is not sorted by ASCII http:/ /blog.csdn.net/zenghui08/article/details/7938975
shell special symbol cut command
- cut split, -d delimiter -f specifies the segment number -c specifies the number of characters
- sort sort, -n sort numerically -r reverse order -t separator -kn1/-kn1,n2
- wc -l count lines -m count characters -w count words
- uniq deduplication, -c counts the number of lines
- tee is similar to >, the redirect is also displayed on the screen
- tr replacement character, tr 'a' 'b', case replacement tr '[az]' '[AZ]'
- split split, -b size (default unit bytes), -l number of lines
cut command
- The cut command is used to cut a string
- Format: cut -d "delimiter" filename
- -d: followed by a split character, the split character is enclosed in double quotes;
- -f: followed by the number of paragraphs of the string
- -c: followed by the first few characters
- Intercept passwd paragraphs 1 to 3
[root@yong-02 test]# head -3 passwd |cut -d ":" -f 1-3
root:x:0
bin:x:1
daemon:x:2- Intercept passwd paragraphs 1 and 3
[root@yong-02 test]# head -3 passwd |cut -d ":" -f 1,3
root:0
bin:1
daemon:2- Truncate the 3rd character
[root@yong-02 test]# head -3 passwd
root:x:0:0:root:/root:/bin/bash
bin:x:1:1:bin:/bin:/sbin/nologin
daemon:x:2:2:daemon:/sbin:/sbin/nologin
[root@yong-02 test]# head -3 passwd |cut -c 3
o
n
e- Truncate the 2nd to the 6th character
[root@yong-02 test]# head -3 passwd
root:x:0:0:root:/root:/bin/bash
bin:x:1:1:bin:/bin:/sbin/nologin
daemon:x:2:2:daemon:/sbin:/sbin/nologin
[root@yong-02 test]# head -3 passwd |cut -c 2-6
oot:x
in:x:
aemon
sort command
- The sort command is used for sorting, the format sort [-t separator] [-kn1, n2] [-nur], n1, n2 refer to numbers
- -t delimiter
- -k Sort by column; use commas for interval range -k3,5
- -n sort numerically
- -r sort in reverse order, sorted from hit to small
- -u deduplicate
- -un The letters starting with the letter will be recognized as repeated content, such as skj1 a weotj will be considered as repeated content, only the digital content will be displayed
- sort does not add any options, from the first line of characters backwards, compares by ASCII code value in turn, and sorts in ascending order
[root@yong-02 test]# vim passwd
adf
123
111
!!!
!jk
lfas
<::
>,
%^
root:x:0:0:root:/root:/bin/bash
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
shutdown:x:6:0:shutdown:/sbin:/sbin/shutdown
halt:x:7:0:halt:/sbin:/sbin/halt
operator:x:11:0:operator:/root:/sbin/nologin
ftp:x:14:50:FTP User:/var/ftp:/sbin/nologin
nobody:x:99:99:Nobody:/:/sbin/nologin
systemd-network:x:192:192:systemd Network Management:/:/sbin/nologin
polkitd:x:999:997:User for polkitd:/:/sbin/nologin
postfix:x:89:89::/var/spool/postfix:/sbin/nologin- Sort by numbers
[root@yong-02 test]# sort -n passwd
<::
>,
!!!
%^
adf
bin:x:1:1:bin:/bin:/sbin/nologin
daemon:x:2:2:daemon:/sbin:/sbin/nologin
ftp:x:14:50:FTP User:/var/ftp:/sbin/nologin
halt:x:7:0:halt:/sbin:/sbin/halt
!jk
lfas
lp:x:4:7:lp:/var/spool/lpd:/sbin/nologin
nobody:x:99:99:Nobody:/:/sbin/nologin
operator:x:11:0:operator:/root:/sbin/nologin
polkitd:x:999:997:User for polkitd:/:/sbin/nologin
postfix:x:89:89::/var/spool/postfix:/sbin/nologin
root:x:0:0:root:/root:/bin/bash
shutdown:x:6:0:shutdown:/sbin:/sbin/shutdown
systemd-network:x:192:192:systemd Network Management:/:/sbin/nologin
111
123- Note: If there are letters or special symbols, they are regarded as 0 by default in numerical sorting.
- reverse sort
[root@yong-02 test]# sort -nr passwd
123
111
systemd-network:x:192:192:systemd Network Management:/:/sbin/nologin
shutdown:x:6:0:shutdown:/sbin:/sbin/shutdown
root:x:0:0:root:/root:/bin/bash
postfix:x:89:89::/var/spool/postfix:/sbin/nologin
polkitd:x:999:997:User for polkitd:/:/sbin/nologin
operator:x:11:0:operator:/root:/sbin/nologin
nobody:x:99:99:Nobody:/:/sbin/nologin
lp:x:4:7:lp:/var/spool/lpd:/sbin/nologin
lfas
!jk
halt:x:7:0:halt:/sbin:/sbin/halt
ftp:x:14:50:FTP User:/var/ftp:/sbin/nologin
daemon:x:2:2:daemon:/sbin:/sbin/nologin
bin:x:1:1:bin:/bin:/sbin/nologin
adf
%^
!!!
>,
<::- To repeat, here the letters are regarded as 0, and then to repeat.
[root@yong-02 test]# sort -nu passwd
adf
111
123
wc command
- The wc command is used to count the number of lines, characters, and words in a document.
- -l count lines
- -m count characters
- -w count words
- View the number of lines in file 1.txt
[root@yong-02 test]# cat 1.txt
abcd
1abcd
123
111
121
[root@yong-02 test]# wc -l 1.txt
5 1.txt- Check how many characters there are in file 1.txt, $ is the end of line character
[root@yong-02 test]# cat -A 1.txt
abcd$
1abcd$
123$
111$
121$
[root@yong-02 test]# wc -m 1.txt
23 1.txt- -w counts words, which are separated by spaces or whitespace characters.
[root@yong-02 test]# cat 1.txt
abcd
1abcd
123
111
121
[root@yong-02 test]# wc -w 1.txt
5 1.txt- If no option is added after wc, and the document is followed directly, the number of lines, words, and characters will be output in turn.
[root@yong-02 test]# cat 1.txt
abcd
1abcd
123
111
121
[root@yong-02 test]# wc 1.txt
5 5 23 1.txtuniq command
- The uniq command is used to remove duplicate lines, usually used in conjunction with sort
- The -c option is more commonly used, it means to count the number of repeated lines and write the number of lines in front
[root@yong-02 test]# cat 2.txt
111
222
123
111
222
adf
123
111
!!!
!jk
lfas
<::
>,
%^
root:x:0:0:root:/root:/bin/bash
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
shutdown:x:6:0:shutdown:/sbin:/sbin/shutdown
shutdown:x:6:0:shutdown:/sbin:/sbin/shutdown
shutdown:x:6:0:shutdown:/sbin:/sbin/shutdown
- Sort first then remove duplicate rows
[root@yong-02 test]# sort 2.txt |uniq -c
1 <::
1 >,
1 !!!
1 %^
3 111
2 123
2 222
1 adf
1 bin:x:1:1:bin:/bin:/sbin/nologin
1 daemon:x:2:2:daemon:/sbin:/sbin/nologin
1 !jk
1 lfas
1 lp:x:4:7:lp:/var/spool/lpd:/sbin/nologin
1 root:x:0:0:root:/root:/bin/bash
3 shutdown:x:6:0:shutdown:/sbin:/sbin/shutdowntee command
- The file name after the tee command is similar to redirection>; but it has one more function displayed on the screen than redirection;
[root@yong-02 test]# cat 1.txt > a.txt
[root@yong-02 test]# cat 1.txt |tee a.txt
abcd
1abcd
123
111
121- tee -a is equivalent to appending redirection >>; it has an additional function of displaying on the screen
[root@yong-02 test]# cat 1.txt |tee -a a.txt
abcd
1abcd
123
111
121
[root@yong-02 test]# cat a.txt
abcd
1abcd
123
111
121
abcd
1abcd
123
111
121
command tr
- tr command is used to replace characters
[root@yong-02 test]# cat 1.txt |tr 'a' 'A'
Abcd
1Abcd
123
111
121
[root@yong-02 test]# cat 1.txt |tr 'a-z' 'A-Z' ##最好'[a-z]' '[A-Z]'
ABCD
1ABCD
123
111
121
split command
- split is used to split the document
- split -l split by line
- split -b split by size
- split -b split by size
[root@yong-02 test]# find /etc/ -type f -name "*.conf" -exec cat {} >test.txt \;
[root@yong-02 test]# du -sh test.txt
240K test.txt
[root@yong-02 test]# split -b 100k test.txt
[root@yong-02 test]# ls
test.txt xab xaa xac
- split -l split by line
[root@yong-02 test]# wc -l test.txt
6082 test.txt
[root@yong-02 test]# split -l 1000 test.txt
[root@yong-02 test]# ls
test.txt xab xad xaf
xaa xac xae xag
- If no file name is specified after split, the split file will be accessed with file names such as xaa, xab...
- Specify the target split file name as abc.
[root@yong-02 test]# split -l 1000 test.txt abc.
[root@yong-02 test]# ls
abc.ab abc.ad abc.af test.txt
abc.aa abc.ac abc.ae abc.ag
special symbols
- $ variable prefix, !$ combination, which means the end of the line
- ; Multiple commands are written 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
- Redirect > Append Redirect >> Error Redirect 2 > Error Append Redirect 2 >> Correct and Error Redirect &>
- [ ] specifies one of the characters, [0-9],[a-zA-Z],[abc]
- || and &&, used between commands
- $: can be used as an identifier in front of a variable, and can be combined with! Used in combination to indicate the end of the line in the regular
[root@yong-02 test]# ls /tmp/gzip/
1.txt 2.txt.zip 4.txt test yyl.tar yyl.tar.gz yyl.zip
2.txt 3.txt 5.txt yyl yyl.tar.bz2 yyl.tar.xz
[root@yong-02 test]# ls !$
ls /tmp/gzip/
1.txt 2.txt.zip 4.txt test yyl.tar yyl.tar.gz yyl.zip
2.txt 3.txt 5.txt yyl yyl.tar.bz2 yyl.tar.xz- ; Multiple commands are written on one line, separated by ;
[root@yong-02 test]# cat 1.txt ;cat a.txt
abcd
1abcd
123
111
121
abcd-
~ home directory, followed by a regular expression match
-
Redirect (correct) > , which overwrites previous content
[root@yong-02 test]# echo "abcdefg" >a.txt
[root@yong-02 test]# cat a.txt
abcdefg- Append redirect (correct) >>
[root@yong-02 test]# echo "1234" >>a.txt
[root@yong-02 test]# cat a.txt
abcdefg
1234- Error redirect 2>
[root@yong-02 test]# cat c.txt 2>a.txt
[root@yong-02 test]# cat a.txt
cat: c.txt: 没有那个文件或目录- error append redirect 2 >>
[root@yong-02 test]# cat c.txt 2>>a.txt
[root@yong-02 test]# cat a.txt
cat: c.txt: 没有那个文件或目录
cat: c.txt: 没有那个文件或目录- &> Errors and corrects are redirected to a file.
[root@yong-02 test]# cat 1.txt c.txt &>a.txt
[root@yong-02 test]# cat a.txt
abcd
1abcd
123
111
121
cat: c.txt: 没有那个文件或目录- link symbol && || in shell;
- && After the previous command is executed successfully, the following command will be executed; if the previous execution is unsuccessful, the latter command will not be executed
- || If the execution of the previous command is unsuccessful, the latter command will be executed; if the execution of the former command is successful, the latter command will not be executed.
- ; Whether the command on the left is successful or not, the following commands will be executed
