Unix: Find all text below string in a file
I recently wanted to parse some text out of a bunch of files so that I could do some sentiment analysis on it. Luckily the text I want is at the end of the file and doesn’t have anything after it but there is text before it that I want to get rid.
The files look like this:
# text I don't care about
= Heading of the bit I care about
# text I care aboutIn other words I want to find the line that contains the Heading and then get all the text after that point.
I figured sed was the tool for the job but my knowledge of the syntax was a bit rusty. Luckily this post served as a refresher.
Effectively what we want to do is delete from the beginning of the file up until the line after the heading. We can do this with the following command:
$ cat /tmp/foo.txt
# text I don't care about
= Heading of the bit I care about
# text I care about$ cat /tmp/foo.txt | sed '1,/Heading of the bit I care about/d'
# text I care aboutThat still leaves an extra empty line after the heading which is a bit annoying but easy enough to get rid of by passing another command to sed that strips empty lines:
$ cat /tmp/foo.txt | sed -e '1,/Heading of the bit I care about/d' -e '/^\s*$/d'
# text I care aboutThe only difference here is that we’re now passing the '-e' flag to allow us to specify multiple commands. If we just pass them sequentially then the 2nd one will be interpreted as the name of a file.
About the author
I'm currently working on short form content at ClickHouse. I publish short 5 minute videos showing how to solve data problems on YouTube @LearnDataWithMark. I previously worked on graph analytics at Neo4j, where I also co-authored the O'Reilly Graph Algorithms Book with Amy Hodler.