简单
" "
huxupeng:~ huxupeng$ echo "
> yan
> c
> 1
> "
yan
c
1
读取
read
echo "hello world"
echo "what is your name?"
read PERSON
echo "hello, $PERSON"
变量
variable=value
variable='value'
variable="value"
大括号
skill="java"
echo "i am learn ${skill}Script"
单引号和双引号
url="https"
web1='c ${url}'
web2="c ${url}"
echo $web1
echo $web2
c ${url}
c https
command
$()
shText=$(cat first.sh)
echo $shText
只读变量
readonly
myName="jack"
readonly myName
myName="rose"
删除变量
unset variable_name
myUrl="http://see.xidian.edu.cn/cpp/u/xitong/"
unset myUrl
echo $myUrl
特殊变量
image.png
命令行参数
sh first.sh a b
#!/bin/bash
echo "File Name: $0"
echo "First Parameter : $1"
echo "First Parameter : $2"
echo "Quoted Values: $@"
echo "Quoted Values: $*"
echo "Total Number of Parameters : $#"
File Name: first.sh
First Parameter : a
First Parameter : b
Quoted Values: a b
Quoted Values: a b
Total Number of Parameters : 2
@ 的区别
2" … "$n" 的形式输出所有参数。
但是当它们被双引号(" ")包含时，"
1
n"的形式输出所有参数；"
1" "
n" 的形式输出所有参数。
#!/bin/bash
echo "\$*=" $*
echo "\"\$*\"=" "$*"
echo "\$@=" $@
echo "\"\$@\"=" "$@"
echo "print each param from \$*"
for var in $*
do
echo "$var"
done
echo "print each param from \$@"
for var in $@
do
echo "$var"
done
echo "print each param from \"\$*\""
for var in "$*"
do
echo "$var"
done
echo "print each param from \"\$@\""
for var in "$@"
do
echo "$var"
done
$*= a b c d
"$*"= a b c d
$@= a b c d
"$@"= a b c d
print each param from $*
a
b
c
d
print each param from $@
a
b
c
d
print each param from "$*"
a b c d
print each param from "$@"
a
b
c
d
转换
-E 选项禁止转义
...
命令替换是指Shell可以先执行命令，将输出结果暂时保存，在适当的地方输出。
command
#!/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"
image.png
#!/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}"
加减乘除
#!/bin/sh
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 != $b ]
then
echo "a is not equal to b"
fi
关系运算符
image.png
bool 运算
image.png
字符串运算
image.png
检测文件属性
image.png
拼接字符串
your_name="qinjx"
greeting="hello, "$your_name" !"
greeting_1="hello, ${your_name} !"
echo $greeting $greeting_1
获取字符串长度
string="abcd"
echo ${#string} #输出 4
提取子字符串
string="alibaba is a great company"
echo ${string:1:4} #输出liba
数组
array_name=(
value0
value1
value2
value3
value4
)
array_name[5]=value5
array_name[7]=value6
echo ${array_name[5]} ${array_name[7]} ${array_name[6]}
获取数组的长度
# 取得数组元素的个数
length=${#array_name[@]}
# 或者
length=${#array_name[*]}
# 取得数组单个元素的长度
lengthn=${#array_name[n]}
显示换行
echo "OK!\n"
echo "It is a test"
显示不换行
echo "OK!\c"
echo "It is a test"
原样输出字符串
echo '$name\"'
显示命令执行结果
echo `date`
显示结果重定向至文件
echo "It is a test" > myfile
printf
# format-string为双引号
$ printf "%d %s\n" 1 "abc"
1 abc
# 单引号与双引号效果一样
$ printf '%d %s\n' 1 "abc"
1 abc
# 没有引号也可以输出
$ printf %s abcdef
abcdef
# 格式只指定了一个参数，但多出的参数仍然会按照该格式输出，format-string 被重用
$ printf %s abc def
abcdef
$ printf "%s\n" abc def
abc
def
$ printf "%s %s %s\n" a b c d e f g h i j
a b c
d e f
g h i
j
# 如果没有 arguments，那么 %s 用NULL代替，%d 用 0 代替
$ printf "%s and %d \n"
and 0
# 如果以 %d 的格式来显示字符串，那么会有警告，提示无效的数字，此时默认置为 0
$ printf "The first program always prints'%s,%d\n'" Hello Shell
-bash: printf: Shell: invalid number
The first program always prints 'Hello,0'
if
#!/bin/sh
a=10
b=20
if [ $a == $b ]
then
echo "a is equal to b"
elif [ $a -gt $b ]
then
echo "a is greater than b"
elif [ $a -lt $b ]
then
echo "a is less than b"
else
echo "None of the condition met"
fi
test
test 命令用于检查某个条件是否成立，与方括号([ ])类似。
test
num1=$[2*3]
num2=$[1+5]
if test $[num1] -eq $[num2]
then
echo 'The two numbers are equal!'
else
echo 'The two numbers are not equal!'
fi
num1=100
num2=100
if test num1=num2
then
echo 'The two strings are equal!'
else
echo 'The two strings are not equal!'
fi
文件测试
cd /bin
if test -e ./bash
then
echo 'The file already exists!'
else
echo 'The file does not exists!'
fi
另外，Shell还提供了与( ! )、或( -o )、非( -a )三个逻辑操作符用于将测试条件连接起来，其优先级为：“!”最高，“-a”次之，“-o”最低。例如：
cd /bin
if test -e ./notFile -o ./bash
then
echo 'One file exists at least!'
else
echo 'Both dose not exists!'
fi
case-esac
echo 'Input a number between 1 to 4'
echo 'Your number is:\c'
read aNum
case $aNum in
1) echo 'You select 1'
;;
2) echo 'You select 2'
;;
3) echo 'You select 3'
;;
4) echo 'You select 4'
;;
*) echo 'You do not select a number between 1 to 4'
;;
esac
for循环
for loop in 1 2 3 4 5
do
echo "The value is: $loop"
done
for str in 'This is a string'
do
echo $str
done
#!/bin/bash
for FILE in $HOME/.bash*
do
echo $FILE
done
while循环
COUNTER=0
while [ ${COUNTER} -lt 5 ]
do
COUNTER=`expr $COUNTER + 1`
echo $COUNTER
done
COUNTER=0
while [ ${COUNTER} -lt 5 ]
do
COUNTER=$(expr $COUNTER + 1)
echo $COUNTER
done
echo 'type <CTRL-D> to terminate'
echo -n 'enter your most liked film: '
while read FILM
do
echo "Yeah! great film the $FILM"
done
break
#!/bin/bash
while :
do
echo -n "Input a number between 1 to 5: "
read aNum
case $aNum in
1|2|3|4|5) echo "Your number is $aNum!"
;;
*) echo "You do not select a number between 1 to 5, game is over!"
break
;;
esac
done
break n
#!/bin/bash
for var1 in 1 2 3
do
for var2 in 0 5
do
if [ $var1 -eq 2 -a $var2 -eq 0 ]
then
break 2
else
echo "$var1 $var2"
fi
done
done
NUMS="1 2 3 4 5 6 7"
for NUM in $NUMS
do
Q=`expr $NUM % 2`
if [ $Q -eq 0 ]
then
echo "Number is an even number!!"
continue
fi
echo "Found odd number"
done
Shell函数
#!/bin/bash
# Define your function here
Hello () {
echo "Url is http://see.xidian.edu.cn/cpp/shell/"
}
# Invoke your function
Hello
带有return语句的函数：
#!/bin/bash
funWithReturn(){
echo "The function is to get the sum of two numbers..."
echo -n "Input first number: "
read aNum
echo -n "Input another number: "
read anotherNum
echo "The two numbers are $aNum and $anotherNum !"
return $(($aNum+$anotherNum))
}
funWithReturn
# Capture value returnd by last command
ret=$?
echo "The sum of two numbers is $ret !"
Shell函数参数
#!/bin/bash
funWithParam(){
echo "The value of the first parameter is $1 !"
echo "The value of the second parameter is $2 !"
echo "The value of the tenth parameter is $10 !"
echo "The value of the tenth parameter is ${10} !"
echo "The value of the eleventh parameter is ${11} !"
echo "The amount of the parameters is $# !" # 参数个数
echo "The string of the parameters is $* !" # 传递给函数的所有参数
}
funWithParam 1 2 3 4 5 6 7 8 9 34 73
Shell文件包含
#!/bin/bash
. ./subscript.sh
echo $url
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