Shell Programming (iii)

Bash basic features: command line expansion

~: Automatically expands to the user's home directory, or the specified user's home directory;

{}: A comma-delimited list of paths can be hosted and can be expanded to multiple paths;

For example:/tmp/{a,b} is equivalent to/tmp/a/tmp/b

Exercise: Create the following directory structure:

/tmp/mysysroot/

|--bin

|--etc

| '--Sysconfig

| '--network-scripts

|--Sbin

|--usr

| |--bin

| |--Lib

| |--lib64

| |--Local

|   | |--bin

|   | |--etc

|   | |--Lib

|   | '--sbin

| '--sbin

'--Var

|--Cache

|--Log

'--run

~]# Mkdir-pv/tmp/mysysroot/{bin,sbin,etc/sysconfig/network-scripts,usr/{bin,sbin,local/{bin,sbin,etc,lib},lib, Lib64},var/{cache,log,run}}

Tree command:

tree [options] [directory]

-L Level: Specifies the hierarchy to display;

Bash's underlying features: command execution status results

Status result of the command execution:

Bash outputs this result with a status return value:

Success: 0

Failed: 1-255

After the command execution completes, its status return value is saved in Bash's special variable $?

When the command executes normally, some return the command value:

Depending on the command and its function, the results are different;

The execution result of the reference command:

$ (COMMAND)

or ' COMMAND '

Bash-based features: references

Strong quote: '

Weak reference: ""

Command reference: '

Bash Basic features: shortcut keys

CTRL + A: Jump to the beginning of the command line

Ctrl+e: Jump to the end of the command line

Ctrl+u: Deletes all the characters from the beginning of the line to the cursor position;

Ctrl+k: Removes all characters from the cursor to the end of the line;

Ctrl+l: Clear screen, equivalent to clear

Shell Programming (iii)