shell基础

第一个shell脚本
#!/bin/bash
echo "Hello World"

使用read从标准输入获取输入并赋值给变量，然后输出
#!/bin/bash

# Author : zjw
# Copyright @ www.litsoft.com
# Script follow here:

echo "what is your name?"
read PERSON
echo "Hello, $PERSON"

使用变量，并使用了for循环
#!/bin/bash

for skill in Ada Coffe Action Java
do
    echo "I am good at ${skill} Script."
done

echo "Over"

重定义变量
#!/bin/bash

myUrl="Http://www.litsoft.com"
echo ${myUrl}

myUrl="Http://www.myblog.com"
echo ${myUrl}

echo "Over"


只读变量
#!/bin/bash

myUrl="Http://www.litsoft.com"
echo ${myUrl}

readonly myUrl

myUrl="Http://www.myblog.com"
echo ${myUrl}

echo "Over"


删除变量
#!/bin/bash

myUrl="Http://www.litsoft.com"
echo ${myUrl}

unset myUrl

#myUrl="Http://www.myblog.com"
echo ${myUrl}

echo "Over"


特殊变量，命令行参数
#!/bin/bash

echo "File Name : $0"
echo "First Parameter : $1"
echo "Second Parameter : $2"
echo "Quoted Values : $@"
echo "Quoted Values : $*"
echo "Total Number of Parameters : $#"


变量替换
#!/bin/bash

a=10
echo -e "Value of a is $a \n"
echo "Over"


命令替换
#!/bin/bash
DATE=date
echo "Date is $DATE"

USERS=who | wc -l
echo "Logged in user are $USERS"

UP=date; uptime
echo "Uptime is &UP"


变量替换
#!/bin/bash

echo ${var:-"Variable is not set"}
echo "1 - Value of var is ${var}"

echo ${var:="Variable is not set"}
echo "2 - Value of var is ${var}"

unset var
echo ${var:+"This is default value"}
echo "3 - Value of var is $var"

var="Prefix"
echo ${var:+"This is default value"}
echo "4 - Value of var is $var"

echo ${var:?"Print this message"}
echo "5 - Value of var is ${var}"


===========================shell运算符============================================
算术运算符
#!/bin/bash

val= expr 2 + 2

echo "Total value : $val"

#!/bin/bash

a=10
b=20
val= expr $a + $b
echo "a + b : $val"

val= expr $a - $b
echo "a - b : $val"

val= expr $a \* $b
echo "a * b : $val"

val= expr $b / $a
echo "b / a : $val"

val= expr $b % $a
echo "b % a : $val"

if [ $a == $b ]
then
    echo "a is equal to b"
fi

if [ $a != $b ]
then
    echo "a is not equal to b"
fi


关系运算符
#!/bin/sh

a=10
b=20
if [ $a -eq $b ]
then
    echo "$a -eq $b : a is equal to b"
else
    echo "$a -eq $b : a is not equal to b"
fi

if [ $a -ne $b ]
then
    echo "$a -ne $b : a is not equal to b"
else
    echo "$a -ne $b : a is equal to b"
fi

if [ $a -gt $b ]
then
    echo "$a -gt $b : a is greater than b"
else
    echo "$a -gt $b : a is not greater than b"
fi

if [ $a -lt $b ]
then
    echo "$a -lt $b : a is less than b"
else
    echo "$a -lt $b : a is not less than b"
fi

if [ $a -ge $b ]
then
    echo "$a -ge $b : a is greater or equal to b"
else
    echo "$a -ge $b : a is not greater or equal to b"
fi

if [ $a -le $b ]
then
    echo "$a -le $b : a is less or equal to b"
else
    echo "$a -le $b : a is no less or equal to b"
fi


布尔运算符
#!/bin/bash

a=10
b=20

if [ $a != $b ]
then
    echo "$a != $b : a is not equal to b"
else
    echo "$a != $b : a is equal to b"
fi

if [ $a -lt 100 -a $b -gt 15 ]
then
    echo "$a -lt 100 -a $b -gt 15 : return true"
else
    echo "$a -lt 100 -a $b -gt 15 : return false"
fi

if [ $a -lt 100 -o $b -gt 100 ]
then
    echo "$a -lt 100 -o $b -gt 100 : return true"
else
    echo "$a -lt 100 -o $b -gt 100 : return false"
fi

if [ $a -lt 5 -o $b -gt 100 ]
then
    echo "$a -lt 100 -o $b -gt 100 : return true"
else
    echo "$a -lt 100 -o $b -gt 100 : return false"
fi


字符串运算符
#!/bin/bash

a="abc"
b="efg"

if [ $a = $b ]
then
    echo "$a = $b : a is equal to b"
else
    echo "$a = $b : a is not equal to b"
fi

if [ $a != $b ]
then
    echo "$a != $b : a is not equal to b"
else
    echo "$a != $b : a is equal to b"
fi

if [ -z $a ]
then
    echo "-z $a : string length is zero"
else
    echo "-z $a : string length is not zero"
fi

if [ -n $a ]
then
    echo "-n $a : string length is not zero"
else
    echo "-n $a : string length is zero"
fi

if [ $a ]
then
    echo "$a : string is not empty"
else
    echo "$a : string is empty"
fi


文件测试运算符
#!/bin/bash

file="/mnt/hgfs/work/mycode/shell/1.sh"

if [ -r $file ]
then
    echo "File has read access"
else
    echo "File does not have read access"
fi

if [ -w $file ]
then
    echo "File has write permission"
else
    echo "File does not have write permission"
fi

if [ -x $file ]
then
    echo "File has execute permission"
else
    echo "File does not has execute permission"
fi

if [ -f $file ]
then
    echo "File is an ordinary file"
else
    echo "This is a spcial file"
fi

if [ -d $file ]
then
    echo "File is a directory file"
else
    echo "This is not a directory file"
fi

if [ -s $file ]
then
    echo "File size is zero"
else
    echo "File size is not zero"
fi

if [ -e $file ]
then
    echo "File exists"
else
    echo "File does not exist"
fi