Shell Command Basic knowledge point

Command history

# Cat/root/.bash_history//place where historical commands are stored

# History//View the number of command histories

# echo $HISTSIZE//View the number of bars that can be saved

# Vim/etc/profile//Change the value of variable histsize "/histsize" to search

# Source/etc/profile//This will make the value we just modified take effect

# vim/etc/profile→ Add histtimeformat= "%y/%m/%d%h:%m:%s" in Histsize to change the format of the output history, for example: 923 2017/06/28 17:56:42 source/etc/profile include what time input can be displayed!!!

# chattr +a ~/.bash_history//Permanently Save the input history (a permission, only allowed to increment, not allowed to delete)

# !! Executes the previous command

#!761//Find command No. 761 command, in command history!

Command completion

Parameter completion, installation bash-completion

Customize the commands you use frequently to improve efficiency: for example:

# alias resnet= ' systemctl restart Network.service '//But this is only stored in memory, if we need long-term use, it will be written in the configuration file, home directory of #. Bash RC

Wildcard characters

# ls *. txt//View all files ending in. txt

# ls 1* //View all Files beginning with 1

# ls ?. TXT//one-character and. txt files

# ls ??. TXT//two characters and. txt files

# ls [0-3].txt//contains 0.txt 1.txt 2.txt 3.txt

# ls [123].txt//contains 1.txt 2.txt 3.txt

Input and output redirection

">"//redirect >> "//Append Content

# cat 12.txt > 22.txt//view 12.txt content and redirect to 22.txt

# cat 12.txt >> 22.txt//view 12.txt content and append (previous content not deleted) to 22.txt

"2>"//Error redirection "2>>"//Error Append redirect

A command that is often used when writing a shell script at a later time:

# ls [12].txt txzzz.txt (without this file) >1.txt 2>b.txt//Put the correct output, output to 1.txt, error output output to B.txt

Pipe symbol, Job control

Pipe break: The output of a command result is passed to the following command;

# cat 1.txt |wc-l; View 1.txt content and give it back to see How many lines of output ~

# cat 1.txt |grep ' AAA '//view 1.txt content and give back grep to find AAA

# Find./-type F | Wc-l//View how many files are in the current directory and then the statistics output

Case: If the IP address is now being configured, when you enter Vim, you find that you forgot the IP address, and then use "Ctrl + Z" to temporarily return to the command line,FG back to the task, perhaps sometimes, background tasks are more, you can use jobs to view and then restore a task using FG+ID , or put a task in the background to continue with BG+ID, One-time put a command in the background to execute, # sleep & , you can use jobs to see.

System built-in variables

# env//View System variables

# Set//View the system's own variables + user-set variables

Custom variables:

# Zhdy=winner//Set Custom variables

# Set | grep zhdy//querying Zhdy in custom variables

# unset Zhdy//Cancel a custom variable

# variable name rules: Letters, numbers underline, the first cannot be a number

# variable values have special symbols that need to be enclosed in single quotation marks.

# a= ' a$bc ' → # echo $a → # A$BC

# a=1;b=2 → #echo $a $b → # 12

# echo $SSH _tty//See which TTY you're under

#export Zhdy=linux//Create a Global environment variable,

environment variable configuration file

System-level environment variables ( never change unless special requirements):

/etc/profile user Environment variables, interaction , login only execution

/ETC/BASHRC user does not have to log on, execution shell is effective

User-level environment variables ( for current users only ):

~/.BASHRC//Customize some aliases alias

~/.bash_profile//Customize some variables. Example: histsize=2000

~/.bash_history//Custom history-related configuration

~/.bash_logout//Custom actions performed after exit

Profile: When the user logs in, it is used to

BASH: A system or user executes some shell

[root@zhdy-02 ~]# echo $PS 1//output to the left of a format

[\u@\h \w]\$

[[email protected] ~]# ps1= ' [\[email protected]\h \w]\$ '//change format to absolute path

[[Email protected] ~] #cd/etc/sysconfig/network-scripts/

[[email protected] /etc/sysconfig/network-scripts]#//has been shown as absolute path!!!

# ps1= ' \[\033[01;32m\]\[email protected]\h\[\033[00m\]:\[\033[01;36m\]\w\[\033[00m\]\$ ' //color format

Of course, this is only a temporary memory, if you want to permanently modify, be sure to enter # VIM/ETC/BASHRC to modify!

This article is from the "Old seven Linux Operations Management" blog, please be sure to keep this source http://asd9577.blog.51cto.com/4291946/1943326

Shell Command Basic knowledge point