Linux Bash Environment configuration

Linux Bash Environment configuration

The environment configuration can be divided into the following: variable type and scope, variable name (definition), configuration file understanding, Undo variable, view (definition) variable, shell login type and configuration file order of action

1. Variable type and scope of action

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:

$? Previous command execution status return value

Number of $# parameters

$* parameter list

[Email protected] parameter list

The $ A command itself, the script itself

2. Variable naming (definition)

Variable naming follows the following rules:

--can only contain letters, numbers, and underscores, and cannot start with a number,

--should not duplicate the existing environment variables in the system

--See the meaning of the name

Variable assignment: variable name = value

such as: Var_name=value equal to both sides can not have spaces

[Email protected] ~]# My=wei

[Email protected] ~]# echo $my

Wei

Note: The relationship between variables and quotation marks:

Single quote ': Strong reference, variable substitution does not occur

Double quote "": Make special symbols effective

Anti-quote ': Reference command

Example:

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3. Configuration file Understanding

Divided by range:

Global configuration:

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

/etc/bashrc

Personal configuration:

~/.bash_profile

~/.bashrc

Classification by functional Category:

Profile class: Provides configuration for the interactive logon shell

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

~/.bash_profile

BASHRC class: Provides configuration for non-interactive logon shell

/etc/bashrc

~/.bashrc

4. Undo Variables

unset name

[Email protected] ~]# unset my

[Email protected] ~]# echo $my

[Email protected] ~]#

Note: Execution status return code (0-255): 0 is correct; 1-255: Error execution 1,2,127 system reservation, special meaning

5. View (define) variables

View Local Variables: Set

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Define environment variables: Export name=value or Declare-x Name=value

Example: Export path= $PATH:/usr/local/apsch/bin

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View environment variables: env, PRINTENV, export

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6. Shell login type and configuration file action order

Shell Logon type action order:

Interactive login:/etc/profile--/etc/profile.d/*.sh---~/.bash_profile--~/.BASHRC---/ETC/BASHRC

Login directly through the terminal;

User Switching implemented by su-l username command;

Non-interactive login: ~/.BASHRC-/ETC/BASHRC-/etc/profile.d/*.sh

A command-line window opens under the graphical interface;

Execute the script;

Su Username;

This article is from the "10,000-hour Law" blog, be sure to keep this source http://daisywei.blog.51cto.com/7837970/1690785

Linux Bash Environment configuration