bash脚本在获取时会产生不同的结果 [英] bash script yields a different result when sourced

问题描述

您能帮我吗，为什么这个脚本在来源(甚至直接在控制台上)时起作用而在脚本上不起作用?

Could you help me, why this script works when sourced (or even directly on console) and does not work on a script?

我已经检查过了，无论如何我都在/bin/中使用相同的bash，并且始终使用4.4.19(1)-release(已通过$BASH_VERSION检查).

I have checked and in any case I'm using the same bash in /bin/ and always 4.4.19(1)-release (checked with $BASH_VERSION).

此外，我尝试删除了shebang，但没有任何变化.

Moreover I tried removing shebang but nothing changes.

#!/bin/bash

fname=c8_m81l_55.fit
bname=${fname%%+(_)+([0-9]).fit}
echo $bname

给出以下结果:

test:~$ ./test.sh
c8_m81l_55.fit

test:~$ . ./test.sh
c8_m81l

推荐答案

除非启用了extglob，并且默认情况下将其禁用，否则Bash无法识别+(pattern)语法.显然，您的bash设置可以在交互式会话中启用它们；这就是为什么您的脚本仅在来自交互式shell的情况下才能工作.

Bash does not recognize +(pattern) syntax unless extglobs are enabled, and they are disabled by default. Apparently your bash setup enables them in interactive sessions; that's why your script works only when sourced in an interactive shell.

要解决此问题，请通过以下命令在脚本中启用extglob:

To fix that, either enable extglobs within the script by this command:

shopt -s extglob

或使用不管外壳的交互性如何都有效的替代方法:

Or use an alternative that works irrespective of shell's interactiveness:

bname=$(sed 's/__*[0-9][0-9]*\.fit$//' <<< $fname)
# with GNU sed it'd look like:
bname=$(sed -E 's/_+[0-9]+\.fit$//' <<< $fname)

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