Linux Learning Record-variables

Local variables

Varname=value scope for the entire bash process

Local variables

Local Varname=value scope is the current code snippet

Environment variables

Export Varname=value scope is the current shell process and its child processes

Positional variables

$1,$2,...

Special variables

$? Previous command execution status return value

echo $?

Two return values for execution results (0-255)

0 performing the correct

1-255 Execution Errors

Undo Variable

unset varname

View current variables

Set

View environment variables in the current shell

Printenv

Env

Export

a=2

B=3

c= $A + $B

Echo $C

2+3

Script: The stack of commands, according to the actual requirements, combined with the command flow control mechanism to implement the source program.

Shebang: Magic number

#!/bin/bash

Linux Learning Record-variables