shell脚本测试 [英] Shell script test

问题描述

我特林更新别人写的一个bash脚本，我已经翻过来一条线，我不知道。

I'm tring to update a bash script written by someone else and I've come accross a line I'm not sure about.

谁能告诉我下面的检查做什么：

Can anyone tell me what the following check does:

if [ :$RESULT != :0,0 ]

我以为它检查在$ result中的一些值，可能与子？

I assume it's checking for some value in $RESULT, possibly with a substring?

任何帮助AP preciated！

Any help appreciated!

推荐答案

命令 [只是命令的别名测试，右方括号只是被语法来糖（命令 [忽略了最后一个参数，如果它是一个右括号），太行实际上读

The command [ is just an alias of the command test, the closing square bracket just being sytax sugar (the command [ ignores the last argument if it's a closing bracket), so the line actually reads

if test :$RESULT != :0,0

它比较，如果该字符串：$结果等于字符串：0,0 。冒号是该变量 $结果是空的情况下prepended。该生产线将类似于以下如果结肠省略 $结果是一个空字符串：

It compares if the string :$RESULT equals to the string :0,0. The colon is prepended for the case that the variable $RESULT is empty. The line would look like the following if the colon was omitted and $RESULT was an empty string:

if test  != 0,0

这将导致一个错误，因为测试预计前参数！= 。另一种方法是用引号，表明有一种说法，这是一个空字符串：

This would lead to an error, since test expects an argument before !=. An alternative would be to use quotes to indicate that there is an argument, which is an empty string:

if test "$RESULT" != 0,0
# Will become
if test "" != 0,0

你贴的变化是更轻便，虽然。

The variation you posted is more portable, though.

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