反转字符串

#!/bin/sh 
#test.sh
STR=$1
LEN=${#STR}
for((i=LEN;i>=0;i--))
do
trap 'echo "第$LINENO行操作之前i=$i"' DEBUG
trap '错误 $LINENO:' ERR
trap 'echo "结尾:"' EXIT
        echo -n ${STR:i:1}
done
echo -e "\n"

运行

./test.sh 123456 > test.txt

123456是传入的参数，将运行结果输出到test.txt文件。

修改后：

fun(){
a=$1
len=${#a}
echo "反转前：$a"
echo "长度是$len"
for((i=$len-1;i>=0;i--))
do
trap 'echo "execute in lineno:$LINENO, the char is ${a:i:1}"' DEBUG
    echo "char:${a:i:1}"
done
echo -e "\n"
}
read -p "please input a word you want to reverse:" str
fun $str > test.txt

效果图

反转字符的同时字符大小写互转，将调试信息保存到log.txt文件中

fun(){
     #获取参数
    a=$1
     #取字符串长度
    len=${#a}
    echo "反转前：$a"
    echo "长度是$len"
     #遍历字符串
    for((i=$len-1;i>=0;i--))
    do
        #从后向前依次取得字符
        c=${a:i:1}
        #清空log.txt
        :>log.txt
        #打印调试信息
        trap 'echo "execute in lineno:$LINENO, the char is $c" >> log.txt' DEBUG
        trap 'error occur in lineno:$LINENO >> test.txt' ERR
        trap 'echo "end:" >> test.txt' EXIT
                #判断字符类型
                case $c in
                        #为大写字母时转为小写
                        [[:upper:]])
                                echo -n  $c | tr [A-Z] [a-z];;
                        #为小写字母时转为大写
                        [[:lower:]])
                                echo -n $c | tr [a-z] [A-Z];;
                        #非字母不需改变
                        *)
                                echo -n "$c" ;;
                esac
    done
    echo -e "\n"
}
#从键盘获取参数
read -p "please input a word you want to reverse:" str
#调用函数
fun $str

测试

查看日志文件