如果不是bash，则与sys.exit()的bash版本合为一行 [英] Bash if else then in one line with bash version of sys.exit()

问题描述

我正在运行此bash命令:

I am running this bash command:

xe pbd-unplug uuid=$PBDUUID

如果结果存在-即如果变量PBDUUID不为空，则我想运行另一个命令:

If the result exists - i.e. if the variable PBDUUID is not empty then I would like to run another command:

xe sr-forget uuid=$SRUUID

但是，如果变量为空，那么我想打印一条错误消息

However, if the variable is blank then I would like print an error message

Error: No PBD.

，然后脚本立即退出(类似于Python中的sys.exit()).

and for the script to exit immediately (similar to sys.exit() in Python).

是否有一种方法可以将此if else then合并为一行?另外，sys.exit()的bash等效项是什么?

Is there a way to combine this if else then into one line? Also, what is the bash equivalent of sys.exit()?

其他信息/评论:

关于Dilettant的评论，是的，该方法(if [ -z ${PBDUUID} ]; then)也将起作用.我不知道.谢谢你看起来很直观.

Regarding comment by Dilettant, yes that approach (if [ -z ${PBDUUID} ]; then) will also work. I was not aware of it. Thanks for this. That seems quite intuitive.

推荐答案

if xe pbd-unplug uuid="$PBDUUID"; then xe sr-forget "uuid=$SRUUID"; else echo "Error: No PBD."; exit 1; fi

更容易理解的是，

if xe pbd-unplug uuid="$PBDUUID"; then
  xe sr-forget "uuid=$SRUUID"
else
  echo "Error: No PBD." >&2
  exit 1
fi

顺便说一句，如果您的目标是检查变量是否为空，则该变量应类似于以下内容:

BTW, if your goal is to check whether a variable is blank, that would look more like the following:

if [ -z "$PDBUUID" ]; then
  xe pdb-unplug uuid="$PDBUUID" && xe sr-forget "uuid=$SRUUID"
else
  echo "Error: No PBD." >&2
  exit 1
fi

---

如果exit并没有按照您的预期进行，则该代码可能在子外壳中运行，因此exit退出了该子外壳，而不是整个脚本.请参阅 SubShell 或创建子Shell的操作"部分. .bash-hackers.org/scripting/processtree"rel =" nofollow> processtree bash-hackers.org页面.

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If exit doesn't do as you intend, then this code is presumably running in a subshell, and thus exit is exiting that subshell rather than your script as a whole. See SubShell or the "Actions that Create a Subshell" section of the processtree bash-hackers.org page.

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