Bash's variables

Bash the variable

(1) name of the variable

Can contain only letters, numbers, and underscores, and cannot begin with a number;

Should not be the same as the existing environment variables in the system;

It's better to see the name and know it.

(2) Variable Type

Local variables: scoped to the current shell process

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

Environment variables: scoped to the current shell process and its child processes

Position variable: $1,$2

Special variables: $?

(3) definition of a variable

Define local variables: name=value

View Local Variables: Set

Defining Environment Variables: exportname=value

Declare–xname=value

View Local Variables: env,printenv,export

Undo Variable: unset name

Reference variable: ${name}, $name

Bash the reference symbol in:

"': strong references, variable substitution does not occur

"" : Weak references

``: Command Reference

Shell Login 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 script

Configuration file Action Order:

Interactive login:

/etc/profile-->/etc/profile.d/*.sh--~/.bash_profile-~/.BASHRC-->/ETC/BASHRC the last priority is the highest .

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: Duplicate variables are generated

Bash's variables