csh习惯用来检查环境变量的存在？ [英] csh idioms to check for environment variable existence?

问题描述

我有几个csh脚本，我需要检查某些环境变量是否在我开始做某些事情之前设置，所以我做这样的事情：

I've got a few csh scripts where I need to check that certain environment variables are set before I start doing stuff, so I do this sort of thing:

if ! $?STATE then
    echo "Need to set STATE"
    exit 1
endif

if ! $?DEST then
    echo "Need to set DEST"
    exit 1
endif

这是很多打字。有没有一个更优雅的成语来检查环境变量是否已经设置？

which is a lot of typing. Is there a more elegant idiom for checking whether or not an environment variable is already set?

注意：

• 是非常相似的，但特别要求bash中的解决方案。


• 我不是在寻找人来建议我远离csh，因为它被诅咒可怕，还是bash都比较好。我特别感兴趣的是比现在使用的更优雅的解决方案。

• This question is quite similar, but specifically asks about solutions in bash.
• I'm not looking for people to advise me to stay away from csh because it's cursed, scary, or bash is better. I'm specifically interested in a more elegant solution than what I'm using now.

推荐答案

我认为你这样做的方式（一个如果语句，条件是使用 $？VAR 语法，如果变量设置为1，则评估为1）否则为0）可能是最惯用的 csh 构造，可以执行所需的操作。

I think the way you're doing it (an if statement with a condition using the $?VAR syntax, which evaluates to 1 if the variable is set, and 0 otherwise) is probably the most idiomatic csh construct that does what you want.

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