Wildcard:

* Any character
 ?: Any single character
 []: Any of them
 [-]: Sequence of a paragraph
 [^]: Not one of them

# Display file names beginning with cron

[root@CentOS ~]# ll /etc/cron*

# Display the filename of exactly five letters under / etc /.

[root@CentOS ~]# ll /etc/?????

# Display the file name with numbers under / etc /.

[root@CentOS ~]# ll /etc/*[0-9]*

# Display file names that do not start with lowercase letters at / etc / below

[root@CentOS ~]# ll /etc/[^a-z]*

# Copy files that are not lowercase letters at the beginning of / etc / to / tmp

[root@CentOS ~]# cp -a /etc/[^a-z]* /tmp

Special symbols in bash:

redirect

Standard input: code 0, using < or <
Standard Output: Code 1, use > or >>.
Standard error output: code 2, 2 > or 2 > after use
 > The original file will be overwritten
 >: Added to the source file
 1 >: Overwrite the specified file with the correct result
 1 >: Append the correct result to the specified document
 2>: Overwrite the error result to the specified file
 2>: Append the error result to the specified file

<: Import by file
 < <: End keyword, end of input

# Store stdout and stderr in different files

[root@CentOS ~]# find /home -name .bashrc > list_right 2> list_error

# Discard the error message and display the correct result on the screen

[root@CentOS ~]# find /home -name .bashrc 2> /dev/null

# Write all the results of the command to the list file (either of the following can be used)

[root@CentOS ~]# find /home -name .bashrc > list 2>&1
[root@CentOS ~]# find /home -name .bashrc &> list 

[root@CentOS ~]# cat > catfile < ~/.bashrc
[root@CentOS ~]# ll catfile ~/.bashrc
-rw-r--r--. 1 root root 176 3month   9 09:24 catfile
-rw-r--r--. 1 root root 176 9month  22 2004 /root/.bashrc

# The two files are the same

# "... "Designate an end sign:

[root@CentOS ~]# cat > catfile << "eof"
> this is a test
> OK noe stop
> eof
[root@CentOS ~]# 

cut select command
Parameters:
- d: Subsequent delimiter for segmentation
- f: According to subparagraph - d, which paragraph should be selected?
- c: Remove fixed character intervals in units of characters

# Show paragraph 5 separated by:

[root@CentOS ~]# echo $PATH | cut -d ':' -f 5

# Separated by: showing 3 and 5 segments

[root@CentOS ~]# echo $PATH | cut -d ':' -f 3,5

# Delete the export information after the 12th character

[root@CentOS ~]# export
declare -x CVS_RSH="ssh"
declare -x USER="kevin"
declare -x USERNAME="kevin"
declare -x WINDOWID="52428804"
declare -x WINDOWPATH="1"
[root@CentOS ~]# export | cut-c 12-
CVS_RSH="ssh"
USER="kevin"
USERNAME="kevin"
WINDOWID="52428804"
WINDOWPATH="1"

grep: Select commands
Parameters:
- a: Find data in the form of text files from binary files
- c: Calculate the number of times a string is found
- i: Ignore case and case
- n: By the way, output line number
- v: Reverse selection
- color=auto: Display the color of the keywords you will find

# Display the line where root appears in last

[root@CentOS ~]# last | grep 'root'

# Display the part of last that does not appear root

[root@CentOS ~]# last | grep -v 'root'

# Take out the last output as long as there is root and display a column

[root@CentOS ~]# last | grep 'root' | cut -d ' ' -f1

# Take out the lines containing MANPATH in / etc/man.config

grep --color=auto 'MANPATH' /etc/man.config

Sort, uniq, wc: sort command
last: This command is used to list information about users who are currently logged in to the system in the past
1 . sort

# Use last to take the output data only to account number and sort them

[root@CentOS ~]# last | cut -d ' ' -f1 | sort

2. uniq: Used to delete duplicate rows and display only one
Parameters:
- i: Ignore case and case
- c: Counting

# Use last to list accounts, take only account columns, sort them and then take only one.

[root@CentOS ~]# last | cut -d ' ' -f1 | sort | uniq

# Use last to list the accounts, only take the account columns, sort out only one, and want to know how many times each person logs in.

[root@CentOS ~]# last | cut -d ' ' -f1 | sort | uniq -c

3. wc: the overall data for calculating output information
Parameters:
- l: List only rows
- w: Number of words only
- m: List only the number of characters

# Statistics / etc/man.config exactly how many words, lines, characters there are

[root@CentOS ~]# cat/etc/man.config | wc

# The total number of people logged in this month

[root@CentOS ~]# ；last | grep [a-zA-Z] | grep -v 'wtmp' | wc -l

# You should know how many accounts are in the account document:

[root@CentOS ~]# cat /etc/passwd | wc -l

Character conversion
1. tr: text substitution
Parameters:
- d: Delete one of the strings
- s: Replace strings

# Delete:from/erc/passwd file

[root@CentOS ~]# cat /etc/passwd | tr -d ' ' 

# Delete line breaks in DOS files (^ M can be replaced by r)

[root@CentOS ~]# cat /root/passwd | tr -d '\r' > /root/passwd/linux

2. col: tab key to space
Parameters:
- x: Turn the tab key into a space key

#Turn tab into a space key

[root@CentOS ~]# cat /etc/man.config | col -x cat -A | more

3. join: Processing data between two files
Parameters:
- t: Default spaces as delimiters and compare the first field
- i: Ignore case and case
- 1: Which field is used to analyze the first file?
- 2: Which field does the second file use to analyze?

# Integrate / etc/passwd and / etc/shadow data as root

[root@CentOS ~]# head -n 3 /etc/passwd /etc/shadow
[root@CentOS ~]# join -t ':' /etc/passwd /etc/shadow

# Integrate the GID of the fourth field of / etc/passwd and the third field of / etc / group, and integrate the two files

[root@CentOS ~]# head -n 3 /etc/passwd /etc/group
[root@CentOS ~]# join -t ':' -1 4 /etc/passwd -2 3 /etc/group

4. paste: paste the two lines together
Parameters:
- d: Subsequent separator, default tab key
- If filename is written as -, it represents standard input

# Paste the same line of / etc/passwd and / etc/shadow together

[root@CentOS ~]# paste /etc/passwd /etc/shadow

# Read / etc/group first. Then paste it with the above question and take out only the third line.

[root@CentOS ~]#  cat /etc/group | paste /etc/passwd /etc/shadow - | head -n 3

5. expand: turn the tab key into a space
Parameters:
- t: Following the number, a tab key represents eight spaces. We can also customize how many spaces a tab key represents.

# Take out the words of / etc/man.config with the first three lines of MANPATH

[root@CentOS ~]# grep '^MANPATH' /etc/man.config | head -n 3

# Continue with the above question and list all the symbols.

[root@CentOS ~]# grep '^MANPATH' /etc/man.config | head -n 3 | cat -A

# To follow the previous question, set the tab key to 6 characters

[root@CentOS ~]# grep '^MANPATH' /etc/man.config | head -n 3 | expand -t 6 - | cat -A

split: Cut command
Parameters:
- b: Cut file size
- l: Cut in rows

# My / etc/passswd has more than 700 KB, if you want to split it into 300 KB files

[root@CentOS ~]# split -b 300k /etc/termcap termcap

# Merge three files into one file

[root@CentOS ~]#  cat termcap* >> termcap

# Use ls-al to output information and record a file every ten lines

[root@CentOS ~]# ls -al / | split -l 10 - lsroot
[root@CentOS ~]# wc -l lsroot