The basic usage of shell scripts

shell script empowerment

chmod 777 file.sh

1, for circulation print array

arr1=(20 21 23 24 25)
arr2=(a b c d e f g)

for i in ${arr1[*]};do
    echo -e $i "\c"
done
echo
for i in ${arr2[@]};do
    echo -e $i "\c"
done
echo
# -e：转义，"\c"：不换行
# for循环遍历数组
# ; 为条件结束符
# do 相当于左花括号
# done 相当于又花括号

2、if、elif、else和if test

arr1=(20 21 23 24 25)
arr2=(a b c d e f g)

if ((${arr1[0]}==$[10]));then
    echo "arr[0]=10"
elif test ${arr1[0]} -eq $[20];then
    echo "arr[0]=20"
elif test ${arr1[0]} -eq 30;then
    echo "arr[0]=30"
else
    echo "arr[0]=-1"
fi

# then 相当于左花括号，然后没有右花括号
# fi为if的字母倒序，表示if语句执行结束

 

3, while the cycle and break

# while循环
n=20
while (($n>10));do
    echo -e $n "\c"
    ((n--))
done

echo
# while true和break
while true;do
    echo -e "$n" "\c"
    ((n--))
if ((n==0));then
    echo "break"
    break
fi
done

4, function

# 声明函数
sum(){
    echo "This is a method!"
    n=0
    for i in 1 2 3;do
        ((n+=i))
    done
    return $n
}
# 执行函数sum
sum
# $? 表示函数返回值
echo $?