如何使用 sed 编辑 bash 调试输出？(bash -x)

Question

#!/bin/bash -x
echo This is a script that has debugging turned on

此脚本输出

+ echo This is a script that has debugging turned on
This is a script that has debugging turned on

我想通过删除或替换它们来摆脱这些 +。我希望 sed 可以解决我的问题 ( sed 's/^\++//g') -- 但这种方法不会影响调试输出行。

通过更多的实验，我发现调试输出似乎被写入 stderr（用./test.sh 2>/dev/null输出然后排除调试行的命令推断出这一点）

有了这些新信息，我希望这能奏效 ./test.sh 2>&1 | sed 's/^\++//g'

但是，唉，我仍然得到相同的不想要的输出：

+ echo This is a script that has debugging turned on
This is a script that has debugging turned on

Answer 1

该+是PS4提示。将其设置为空字符串：

#!/bin/bash

PS4=''
set -x

echo 'This is a script that has debugging turned on'

测试：

$ bash script.sh
echo 'This is a script that has debugging turned on'
This is a script that has debugging turned on

或者，使用您的原始脚本，PS4在调用脚本时将其设置为空字符串：

$ PS4='' ./script.sh
echo This is a script that has debugging turned on
This is a script that has debugging turned on

这可用于插入时间戳：

$ PS4='$(date +"%T: ")' ./script.sh
21:08:19: echo 'This is a script that has debugging turned on'
This is a script that has debugging turned on
21:08:19: echo 'Now sleeping for 2 seconds'
Now sleeping for 2 seconds
21:08:19: sleep 2
21:08:21: echo Done
Done

Answer 2

您遇到的主要限制+是扩展正则表达式功能，因此您需要启用扩展正则表达式功能；对于大多数seds，那就是-E标志：

./test.sh 2>&1 | sed -E 's/^\++ //'

我做了另外两个改变：

• 添加了尾随空格，以便调试的命令显示为左对齐
• 删除了/g标志，因为正则表达式是锚定的，每行只能有一个匹配项