Linux Learning Note--bash command and Shell variable introduction

Bash and its features

Shell Shell

Gui:gnome KDE Xface

Cli:shell CSH Ksh Bash

Program, Process

Process: Each process appears to have only kernel and current processes present on the current host

A process is a copy of a program, and a process is a program execution instance

User's working environment:

Bash:

# root User

$ normal User

Shell, child shell

Bash:

1. Command history

2. Piping, redirection

3. Command-line editing

4. Command aliases

5. Command line expansion

6. File name Wildcard

7. Variables

8. Programming

Tips for command exercise:

Ctrl + A cursor jumps to the top

Ctrl + e cursor jumps to the end of a career

CTRL + u delete the cursor to the beginning of the content

Ctrl + k Delete cursor to end of line content

Ctrl +l for Clear screen

Command history Usage Tips:

!n executing the nth line command in the command history

!-n execution of the penultimate line command in the history command

!! Executes the previous command

! CHARACTER the last command in the history command that starts with CHARACTER

!$ references the last parameter of the previous command

ESC Release Press. Reference the last parameter of the previous command

TAB key function:

Command completion: Searches for executable files at the beginning of each path specified by the PATH environment variable with the string we give

Path completion: Search for each file name under the starting path that we gave me, and try to complement the whole

Command aliases:

#alias cmdalias=comand Command Rename

Aliases defined in the shell are valid only in the current shell life cycle, the valid range of aliases the current shell process

#unalias Cancel Command Rename, #unalias COMAND

The quotes and functions that bash supports:

' anti-quotes, command substitution

"" Double quotes, weak references, you can complete the variable substitution

' Single quotes, strong references, non-complete variable substitution

Command substitution

The process of replacing a subcommand in a command with the result of a command execution

#echo "The directory is $ (PWD)"

#touch./file-$ (date +%f-%h-%m-%s). txt = = #touch./file-' date +%f-%h-%m-%s'. txt, same functionality

Command history:

#history

[[email protected] skel]# help historyhistory: history [-c] [-d  Offset]  [n]  or  history -anrw [filename]  or  history -ps  parameter  [parameter ...]      display or manipulate the history list.          Show History list with line numbers and prefix each modified entry with   ' * '.      parameters  N  lists only the last  N  entries.          Options:      -c          Delete all entries to clear the history list.       -d         offset   Delete History list from specified location.           -a         Append the history line of the current painting to the history file       -n         Read all unread rows from the history file       -r         Reads the history file and appends the contents to the History list    &NBsp;  -w         writes the current history to the history file   and appends to the history list 

Environment variables:

Path command paths

histsize Command History size

Example: # echo $HISTSIZE, showing the size of the cache command

#echo $shell to display the user shell environment

File name wildcard, globbing

* matches any character of any length, including an empty #ls *

? Match any single character, #ls? y*

[] matches any single character within the specified range, such as [A-za-z][0-9][0-9a-za-z]

[[: Space:]] all whitespace characters

[[:p UNCT:]] all punctuation

[[: Lower:]] all lowercase characters

[[: Upper:]] all uppercase characters

[[: Alpha:]] all uppercase and lowercase letters

[[:d Igit:]] All numbers

[[: Alnum:]] numbers and uppercase and lowercase

[^] matches any single character outside the specified range

Example #ls[[:alpha:]]*[[:space:]]*[[:alpha:]], displaying a file that starts with a letter and ends with a letter and contains spaces in the middle

The type of shell that stands in terms of user login

Log-in Shell

Log in normally via a terminal

Su-username

Su-l USERNAME

Non-sign-on shell

Su USERNAME

Command window open under graphical terminal

Shell scripts that are executed automatically

Bash's configuration file

Global configuration

/etc/profile,/etc/profile.d/*.sh,/ETC/BASHRC

Personal configuration

~/.bash_profile, ~/.BASHRC

File for Profile class

Setting Global environment variables

Sign in to run a command or script

Files for bash classes

Setting Local Variables

Defining command aliases

How the login shell reads the configuration file

/etc/profile--->/etc/profile.d/*.sh---> ~/.bash_profile-->~/.bashrc-->/ETC/BASHRC

Non-sign-on shell

~/.bashrc-->/etc/bashrc-->/etc/profile.d/*.sh

This article is from the "Wish_" blog, be sure to keep this source http://itwish.blog.51cto.com/11439802/1963152

Linux Learning Note--bash command and Shell variable introduction