Shell脚本入门

基础

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declare -r TITLE="Page Title" #常量
a=z
b="a string"
c="a string and $b"
d="$(ls -l foo.txt)"
e=$((5*7))
f="\t\ta string\n"
mv "$filename" "${filename}1"

$? #上次命令的退出状态

echo $foo

cat<<__EOF__ #here document 引号不用转义
    $foo #some text
    "$foo" #"some text"
    '$foo' #'some text'
    \$foo #$foo
__EOF

function funct_2(){
    local foo; #局部变量
    foo=2;
    echo "foo=$foo"
}
echo $(funct_2)

clear
sleep 1

if

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x=5
if ["$x" -eq 5]; then
    echo "5" 
elif ["$x" -eq 6]; then
    echo "6"
else
    echo "no"
fi

常用文件表达式：

表达式 为真情况
-e file 存在
-f file 普通文件
-d file 目录
-r file 可读
-w file 可写
-x file 可执行

常用字符串表达式：

表达式 为真情况
string 不为空
-n string 长度>0
-z string 长度=0
string1==string2或string1=string2
string1!=string2
string1<string2
string1>string2

整数表达式：

表达式 为真情况
-eq
-ne
-le
-lt
-ge
-gt

组合表达式：

操作 test [[]]和(())
and -a &&
or -o ||
not ! !

test增强

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if [["$INT" =- ^-?[0-9]+$ ]]; then #如果匹配正则表达式
    #...
fi

if ((INT==0)); then
    #...
fi

控制操作符

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[[-d temp]] || mkdir temp

输入

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echo -n "input->" #-n不输出结尾换行符
read int1 int2 int3
echo $int1

#!/bin/bash
if read -t 10 -sp "input>" secret_pass; then
    echo -e "\npassphrase='$secret_pass'"
else
    echo -e "\ntimeout" >&2
    exit 1
fi

IFS

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#!/bin/bash
FILE=/etc/passwd
read -p "username>" user_name
file_info="${grep "^$user_name:" $FILE)"
if [-n "$file_info"]; then
    IFS=":" read user pw uid gid name home shell <<< "$file_info" #冒号分开
    echo "User='$user'"
    echo "UID='$uid'"
    echo "GID= '$gid'"
    echo "Full Name='$name'"
    echo "Home DIr='$home'"
    echo "Shell='$shell'"
else
    echo "no such user '$user_name'" >&2
    exit 1
fi

验证输入

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#文件名是否有效
if [["$REPLY"=-^[-[:alnum:]\._]_$]]; then
#是否浮点数
if [["$REPLY"=-^-?[[:digit:]]*\.[[:digit:]]+$]]; then
#是否整数
if [["$REPLY"=-^-?[[:digit:]]+$]]; then

while/until

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count=1
while [["$count" -le 5]]; do
    echo "$count"
    count=$((count+1))
done

#break continue略

count=1
until [["$count" -gt 5]]; do
    echo "$count"
    count=$((count+1))
done

case

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case "$REPLY" in
    0)	echo "xxx" #可正则
        exit
        ;;& #passthrough语法
    1)	echo "xxx"
        uptime
        ;;
    -h|--help)
        usage
        exit
        ;;
    *)	echo "xxx" >&2
        exit 1
        ;;
esac

命令行参数

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echo "$#" #命令行传参个数
echo $0 $1 $2 ...

count=1
while [[$# -gt 0]]; do
    echo $1
    count=$((count+1))
    shift
done

#"word" "words with spaces"
echo $*
    #word
    #words
    #with
    #spaces
echo "$*":
    #word words with spaces
    #
    #
    #
echo $@:
    #同$*
echo "$@":
    #word
    #words with spaces
    #
    #

for

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for i in {A..D}; do
    echo $i;
done

for i in distros*.txt; do
    echo "$i";
done

for ((i=0;i<5;i=i+1)); do
    echo $i
done

字符串与数字

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echo ${foo:-"substitute value if unset"}
echo ${foo:?"parameter is empty"}
echo ${foo:+"substitute value if set"}
echo ${!BASH*} #BASH开头的环境变量
echo ${#foo} #字符串长度
echo ${foo:5:6} #5开始的6个字符

foo=file.txt.zip
echo ${foo#*.} #删除模式*.匹配的后缀 最短
echo ${foo##*.} #同上 最长
echo ${foo%*.} #保留模式*.匹配的后缀 最短
echo ${foo%%*.} #同上 最长

foo=JPG.JPG
echo ${foo/JPG/jpg} #jpg.JPG
echo ${foo//JPG/jpg} #jpg.jpg
echo ${foo/#JPG/jpg} #jpg.JPG
echo ${foo/%JPG/jpg} #JPG.jpg

foo=aBc
echo ${foo,,} #abc 全部小写
echo ${foo,} #aBc 仅第一个小写
echo ${foo^^} #ABC 全部大写
echo ${foo^} #ABc 仅第一个大写

echo $((0xff))
echo $((2#11111111))

数组

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a[1]=foo
echo ${a[1]}

declare -a a

days=(Sun Mon Tue Wed Thu Fri Sat)
days=([0]=Sun [1]=Mon [2]=Tue [3]=Wed [4]=Thu [5]=Fri [6]=Sat)

for i in $(animals[*]); do echo $i; done
for i in $(animals[@]); do echo $i; done
for i in "$(animals[*])"; do echo $i; done #拼接为一个字符串
for i in "$animals[@]"; do echo $i; done

echo ${#a[@]}

foo=([2]=a [4]=b [6]=c)
for i in "$(!foo[@])"; do echo $i; done #当索引不连续时查找索引
unset 'foo[2]'

foo=(a b c)
foo+=(d e f)

a=(f e d c b a)
a_sorted=($(for i in "$a[@]"; do echo $i; done | sort))
unset a

declare -A colors
colors["red"]="#ff0000"
echo ${colors["blue"]}