shell语法

1. 数组

#定义数组
array=("163" "21cn" "sina" "qq")

#获取数组长度
echo ${#array[*]}

#遍历数组
for arr in ${array[*]}; do
  echo $arr
done

# 使用typeset后必须重新赋值才起作用

typeset -u content #upper
content="Show Me The Money"
echo $content

typeset -l content #lower
content="Show Me The Money"
echo $content

# 使用tr
content="Show Me The Money"
new_content=`tr '[a-z]' '[A-Z]' <<< "$content"`
echo $new_content

new_content=`tr '[A-Z]' '[a-z]' <<< "$content"`
echo $new_content

content="Show Me The Money"
new_content=$(echo "$content" | tr '[a-z]' '[A-Z]')
echo $new_content

new_content=$(echo "$content" | tr '[A-Z]' '[a-z]')
echo $new_content

3. 变量替换

${variable:-value}
当variable为空时,替换为value

${variable:+value}
当variable有值时,替换为value

${variable:=value}
当variable为空时,替换并赋值为value

${variable:?message}
当variable为空时,退出脚本,并标准错误输出message

${param#word}
从param头部开始删除到word匹配的最小部分,然后返回剩余的部分
${param##word}
从param头部开始删除到word匹配的最大部分,然后返回剩余的部分
${param%word}
从param尾部开始删除到word匹配的最小部分,然后返回剩余的部分
${param%%word}
从param尾部开始删除到word匹配的最大部分,然后返回剩余的部分

file="/home/fdipzone/shell/command.class.sh"
echo ${file#*/}  # home/fdipzone/shell/command.class.sh
echo ${file##*/} # command.class.sh
echo ${file%/*}  # /home/fdipzone/shell
echo ${file%%/*} # 空
echo ${file#*.}  # class.sh
echo ${file##*.} # sh
echo ${file%.*}  # /home/fdipzone/shell/command.class
echo ${file%%.*} # /home/fdipzone/shell/command
echo ${file/sh/php} # /home/fdipzone/phpell/command.class.sh
echo ${file//sh/php} # /home/fdipzone/phpell/command.class.php 替换多个 

set -n #不执行脚本，只检查语法错误
set -v #在执行命令之前回显
set -x #在执行命令之后回显
set -u #如果使用了未定义变量，给出错误提示。

cat <<!fdipzone!
Hello Wolrd
Shell Ok
!fdipzone!

$$ Shell本身的PID（ProcessID）
$! Shell最后运行的后台Process的PID
$? 最后运行的命令的结束代码（返回值）
$- 使用Set命令设定的Flag一览
$* 所有参数列表。如"$*"用「"」括起来的情况、以"$1 $2 … $n"的形式输出所有参数。
$@ 所有参数列表。如"$@"用「"」括起来的情况、以"$1" "$2" … "$n" 的形式输出所有参数。
$# 添加到Shell的参数个数
$0 Shell本身的文件名
$1～$n 添加到Shell的各参数值。$1是第1参数、$2是第2参数

#!/bin/bash

echo "dirname:$(dirname $0)"

echo "basename:$(basename $0)"

exit 0

#!/bin/bash

# read命令 -p(提示语句) -n(字符最多个数) -t(等待时间) -s(不回显)

TIMEOUT=5

printf "Please input a number: "
read -t "$TIMEOUT" number

if [ "$number" ]; then
	printf "number is: $number\n"
else
	printf "\nnot input number\n"
fi

read -s -n10 -p "Please input the password:" password
printf "\nPassword is: $password\n"

exit 0

#!/bin/bash

DEBUG=true

function debug(){
	"$DEBUG" && echo $(tput setaf 1;)"DEBUG >>>"$(tput sgr0)" $*"
}

debug 'file not exists'

exit 0

#!/bin/bash

function print_info(){

cat <<!INFO!

Usage: myscript <command>

Version: $1

Available Commands

  start:   start worker

  stop:    stop worker

  restart: restart worker

!INFO!

}

print_info 1.0

exit 0

#!/bin/bash

NORMAL=$(tput sgr0)
GREEN=$(tput setaf 2; tput bold; tput setab 5)
YELLOW=$(tput setaf 3; tput setab 4)
RED=$(tput setaf 1)

function red(){
	echo "$RED$*$NORMAL"
}

function green(){
	echo "$GREEN$*$NORMAL"
}

function yellow(){
	echo "$YELLOW$*$NORMAL"
}

green "Task has been completed"

red "The configuration file does not exist"

yellow "You have to use higher version."

exit 0

12. 生成指定位数的随机密码 

# 生成8位随机密码
cat /dev/urandom | head -n 1 | md5sum | head -c 8

date +%N | md5sum | head -c 8

13. 截取字符串

var='1234567890abcdefg'
echo ${var:3:10} # 从字符串第3位开始截取,截取10个字符,输出4567890abc