[Linux] shell脚本错误检测

超、凢脫俗 2023-06-27 12:49 10阅读 0赞

除了 echo 命令，还可以使用如下两种方法。

1.shell跟踪选项

set命令执行之后的每一条命令以及加在命令行中的任何参数（包括变量和变量的值）都会显示出来。"+"是跟踪输出的标志，在子shell中执行的shell命令会加两个"+"。

【例】

#!/bin/sh
    #set -x
    echo -n "Can you write device drivers?"
    read answer
    answer=`echo $answer | tr [a-z] [A-Z]`
    if [ "$answer" = "Y" ]
    then
        echo "Wow, you must be very skilled"
    else
        echo "Neither can I, I'm just an example shell script"
    fi

说明：  
1.read命令参考 https://www.cnblogs.com/anay/p/8973510.html\#\_label0  
2.echo $answer | tr \[a-z\] \[A-Z\]  将变量answer中的小写字母全部转换成大写字母   
3.注意判断式 if \[ "$answer" = "Y" \] 的比较操作符两边都要有空格

运行该文件时,示例结果如下  
$ ./example  
Can you write device drivers? y  
Wow, you must be very skilled

或者  
$ ./example  
Can you write device drivers? n  
Neither can I, Im just an example shell script

如果"set -x"那一行没有注释掉,则运行结果如下所示:  
$ ./example

\+ echo -n 'Can you write device drivers?'  
Can you write device drivers?+ read answer  
y  
\++ echo y  
\++ tr '\[a-z\]' '\[A-Z\]'  
\+ answer=Y  
\+ '\[' Y = Y '\]'  
\+ echo 'Wow, you must be very skilled'  
Wow, you must be very skilled

或如下所示:

\+ echo -n 'Can you write device drivers?'  
Can you write device drivers?+ read answer  
n  
\++ echo n  
\++ tr '\[a-z\]' '\[A-Z\]'  
\+ answer=N  
\+ '\[' N = Y '\]'  
\+ echo 'Neither can I, I'\\''m just an example shell script'  
Neither can I, I'm just an example shell script

2.根据调试层次控制输出

在脚本的开始部分设置一个调试变量。脚本运行时测试该变量，然后根据变量的值决定是显示还是禁止调试指令。

# !/bin/sh
    debug=1
    test $debug -gt 0 && echo "Debug is on"
    echo -n "Can you write device drivers?"
    read answer
    test $debug -gt 0 && echo "The answer is $answer"
    answer=`echo $answer | tr [a-z] [A-Z]`
    if [ "$answer" = "Y" ]
    then
        echo "Wow, you must be very skilled"
        test $debug -gt 0 && echo "The answer is $answer"
    else
        echo "Neither can I, I'm just an example shell script"
        test $debug -gt 0 && echo "The answer is $answer"
    fi

说明：

test $debug -gt 0 && echo some\_debug\_output  只有test结果为真，测试条件逻辑与才会执行其它代码  
test $debug -gt 0 || echo some\_debug\_output  只有test结果为假，测试条件逻辑或才会执行其它代码

参考资料：《shell脚本专家指南》 \[美\] Ron Peters 著