Linux Bash Basics

Bash Environment configuration:

configuration file, the scope of effective, there are two categories:

Global configuration:

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

Personal configuration:

~/.bash_profile, ~/.BASHRC

By function, there are two categories:

Profile class: Provides configuration for the interactive logon shell

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

~/.bash_profile

Function:

(1) Define environment variables, such as path, PS1

(2) run a command or script

BASHRC class: Provides configuration for non-interactive logon shell

/etc/bashrc

~/.bashrc

Function:

(1) Define command aliases;

(2) define local variables;

Variables: Memory space, variable name

Type:

Environment variables: scope current shell process and its child processes

Local variable: scope current shell process

Local variables: scoped only to a snippet of code in the current shell process (usually a function context)

Position variable: $ $, $

Special variables: $? ( The return result of the previous command, normal is 0, the other is wrong )

How variables are defined:

Bash built-in variables: can be called directly, built in a number of environment variables, such as Path

Custom variables:

Variable assignment: variable name = value

Bash Weak type:

When a variable stores data, it is written by default, and any variable can be directly referenced without being declared;

120 (character type): 3byte

120 (numeric type): 1byte

Note: This is also the case in PHP.

To define a local variable:

Name=value

View: Set

Define Environment variables:

Export Name=value

Declare-x Name=value

View: env, printenv, export

Undo Variable:

unset name

Reference variable:

${name}, $name

Reference symbols in bash:

': Strong reference, variable substitution does not occur

"": Weak reference

": Command Reference

Shell Logon Type:

Interactive login:

Login directly through the terminal;

User Switching implemented by su-l username command;

Non-interactive logon:

A command-line window opens under the graphical interface;

Execute the script;

Su Username;

Configuration file Action Order:

Interactive login:

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

Non-interactive logon:

~/.BASHRC--/ETC/BASHRC-/etc/profile.d/*.sh

How does the new configuration of the Edit profile definition take effect?

(1) Re-login;

(2) Let the current shell process to re-read the specified configuration file;

Source/path/to/somefile

. /path/to/somefile

Note: It is possible to cause side effects

actual combat:

1. Define aliases that are valid for all uses?

Answer: just VIM/ETC/BASHRC

2. What if only the modification of the PATH environment variable takes effect for the root user?

Answer:vim ~/.BASHRC can modify the path variable

This article is from the "Wind Rhyme" blog, please be sure to keep this source http://chinalx1.blog.51cto.com/2334265/1691665

Linux Bash Basics