linux shell script

Hello World

#!/bin/bash
echo 'Hello Bash World'

for loop in one line 一行实现循环调用

for i in {1..5}; do COMMAND1-HERE && COMMAND2-HERE; done

定义function

你可以用function 函数名{}
或者 直接函数名

#!/bin/bash
#usage(){
function usage(){
	echo "sleep seconds"
}

if [ $# == 1 ]; then
	getSomeSleep $1
else
	usage
fi

逻辑表达式详解

input parameters

• $# 是传给脚本的参数个数
• $0 是脚本本身的名字
• $1是传递给该shell脚本的第一个参数
• $2是传递给该shell脚本的第二个参数
• $@ 是传给脚本的所有参数的列表

ref link

if [ $# -lt 1 ];then
        usage
        exit 1
fi

function parameters

function getSomeSleep(){
            SLEEP_SEC=$1
            SLEEP_MAX_SEC=30
            #minus=`echo $SLEEP_SEC/1 | bc`
            if [ $SLEEP_SEC -gt 0 ] && [ $SLEEP_SEC -lt 30 ]; then
                echo '###################'
                echo 'now try to restart node after ' $SLEEP_SEC ' sec'
                echo '###################'
                sleep $SLEEP_SEC
            else
                echo 'sec must between 0 and ' $SLEEP_MAX_SEC ' sec'
            fi  
    }

注意输入参数在函数中, $0 $1 $2 .. $@会被覆盖，但$#不会

call from another script file

直接输入绝对路径或者相对路径

. -- execute

part 2 going deep: Beauty/Standard

option

case

case 实现效果：
$haproxy status/stop/start/reload/restart

case 语法 github example

option

getopt 实现效果：
$SomeCommand -p 223  -h localhost

opt 语法 github example

help

定义 usage function, 处理-h --help

man

实现效果：
$man 1 sleep1

edit man page file ,then put it in :
/usr/share/man/man1

$sudo cp sleep.sh /bin/sleep1
#see example 
$man 1 sleep1

man 1/2/3/.. 7 的[差别][5]

section 	topic
1	Executable programs or shell commands
2	System calls (functions provided by the kernel)
3	Library calls (functions within program libraries)

exit code

$ ./sleep.sh 2 3
usage: sleep seconds
#上一个命令的执行效果,来自于shell script 文件的exit code

$ echo $?
1
$ echo $?
0

path

put your file to $PATH

part 3 going deep: use bash to improve efficiency

alias

alias file example

• git push origin/ ==> gpo
• find ./* -name ==> f "*.md"
• ...

bin

去扫以下各个文件夹：

$ echo $PATH
/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin

path env

grep egrep awk

regex

fucksh zash

tips

经常忘记sudo，快速根据上一个命令重新执行

$apt-get install tree
$sudo !!

写错命令，快速根据上一个命令的参数重新执行

klg@klgaliyun01:~$ vim /etc/init.d/haproxy 
klg@klgaliyun01:~$ cat !$
cat /etc/init.d/haproxy

开机启动文件 /etc/rc.local

when system start , run this script

~/.bash_profile ~/.bashrc

when user login, run this script

mount to shared drive

UI Color : make terminal more colorful, tell the diff between dir and file, the diff between execute and unexecute

export CLICOLOR=1
export LSCOLORS=Exfxcxdxbxegedabagacad
# Tell grep to highlight matches
export GREP_OPTIONS='--color=auto'
export TERM="xterm-color"
PS1='[e[0;33m]u[e[0m]@[e[0;32m]h[e[0m]:[e[0;34m]w[e[0m]$ '

copy past without mousee

pbcopy < somefile
pbpaste > somefile_copy 

pipe line and redirect

# pipe line
| # left output as right output
> >>  
< <<
2> #stderr redirect 
$somecommand >> file.out.log 2>1 & ## stderr redirect to stdout , then redirect to some file
$ ls x* z* 2>/dev/null  ##output redirect to device : /dev/null ## black hole, which means  ignore the output

![stdin stdout stderr][7]
[linux pipe line and redirect][8]
[IBM pipe line pdf][9]

坑

注意空格：in if then else fi

if [ xx -lt 0 ];
   ...

还是注意空格：PID=123 ##not PID = 123 

debug

$bash -x xxx.sh
[debug example][10]

常用Linux shell 集合