在bash脚本中使用标志

Question

linux中的脚本以一些声明开头:

#!/bin/bash

如果我错了,请纠正我:这可能说明要使用哪个shell.

我还看到一些脚本说:

#!/bin/bash -ex

标志-ex的用途是什么？

Answer 1

#!/bin/bash -ex

<=>

#!/bin/bash
set -e -x

Man Page(http://ss64.com/bash/set.html):

-e  Exit immediately if a simple command exits with a non-zero status, unless
   the command that fails is part of an until or  while loop, part of an
   if statement, part of a && or || list, or if the command's return status
   is being inverted using !.  -o errexit

-x  Print a trace of simple commands and their arguments
   after they are expanded and before they are executed. -o xtrace

更新:

顺便说一句,可以在没有脚本修改的情况下设置开关.

例如,我们有脚本t.sh:

#!/bin/bash

echo "before false"
false
echo "after false"

并想跟踪这个脚本: bash -x t.sh

output:

 + echo 'before false'
 before false
 + false
 + echo 'after false'
 after false

例如,我们想跟踪脚本并在某些命令失败时停止(在我们的例子中,它将通过命令完成false):bash -ex t.sh

output:

+ echo 'before false'
before false
+ false