如何在perl中查找和替换多行文本

Question

I have a text file named "data" with the content:

a
b
c
abc

I'd like to find all "abc" (doesn't need to be on the same line) and replace the leading "a" to "A". Here "b" can be any character (one or more) but not 'c'.

(This is a simplification of my actual use case.)

I thought this perl command would do

perl -pi.bak -e 's/a([^c]+?)c/A\1c/mg' data

With this 'data' was changed to:

a
b
c
Abc

I was expecting:

A
b
c
Abc

I'm not sure why perl missed the first occurrence (on line 1-3).

Let me know if you spot anything wrong with my perl command or you know a working alternative. Much appreciated.

Answer 1

You're reading a line at a time, applying the code to that one line. It can't possibly match across multiple lines. The simple solution is to tell perl to treat the entire file as one line using -0777 .

perl -i.bak -0777pe's/a([^c]+c)/A$1/g' data

• Replaced the incorrect \\1 with $1 .
• Removed the useless /m . It only affects ^ and $ , but you don't use those.
• Removed the useless non-greedy modifier.
• Moved the c into the capture to avoid repeating it.