grep substring between two delimiters

regex bash perl grep busybox
Ulrik picture Ulrik · Oct 13, 2014 · Viewed 17k times · Source

I have a lot of bash scripts that use perl expressions within grep in order to extract a substring between two delimiters. Example:

echo BeginMiddleEnd | grep -oP '(?<=Begin).*(?=End)'

The problem is, when I ported these scripts to a platform running busybox, 'integrated' grep does not recognize -P switch. Is there a clean way to do this using grep and regular expressions?

Edit: There is no perl, sed or awk on that platform. It's a lightweight linux.

Answer

anubhava picture anubhava · Oct 13, 2014

You can use awk with custom field separator like this to get same output:

echo 'BeginMiddleEnd' | awk -F 'Begin|End' '{print $2}'
Middle

Related questions

Positive/Negative lookahead with grep and perl

my login.txt file contains following entries abc def abc 123 def abc abc de tha ewe when i do the positive lookahead using perl, i'm getting the following result cat login.txt | perl -ne 'print if /(?)abc\s(?=def)/' …

Read More
Find and kill a process in one line using bash and regex

I often need to kill a process during programming. The way I do it now is: [~]$ ps aux | grep 'python csp_build.py' user 5124 1.0 0.3 214588 13852 pts/4 Sl+ 11:19 0:00 python csp_build.py user 5373 0.0 0.0 8096 960 pts/6 S+ 11:20 0:00 grep python csp_build.py [~]$ kill 5124 How …

Read More
Check if a string matches a regex in Bash script

One of the arguments that my script receives is a date in the following format: yyyymmdd. I want to check if I get a valid date as an input. How can I do this? I am trying to use a …

Read More