regex - grep 前一行仅针对一种特定模式

Question

给出一个示例日志文件，例如:

interesting stuff
App: 123 blob
some text
other text
ERROR could not find file XYZ
other really cool stuff
App: 123 blob
some text
other text
ERROR stdout blocked

我想用 'ERROR' 和 'App:' 加上 'App:' 之前的行来 grep 行。 使用多个搜索模式和 -B 1 我得到匹配行以及之前的相应行:

grep -B 1 -e '^App:.*' -e '.*ERROR.*'

interesting stuff
App: 123 blob
--
other text
ERROR could not find file XYZ
other really cool stuff
App: 123 blob
--
other text
ERROR stdout blocked

(我也不知道“--”来自哪里) 但我想要的输出是:

interesting stuff
App: 123 blob
ERROR could not find file XYZ
other really cool stuff
App: 123 blob
ERROR stdout blocked

非常感谢。

Answer 1

grep 的 -B 1 选项将应用于所有表达式。在这种情况下，您可以使用 awk:

$ awk '/App/ {print line;print} {line=$0} /ERROR/' file 
interesting stuff
App: 123 blob
ERROR could not find file XYZ
other really cool stuff
App: 123 blob
ERROR stdout blocked
$