Bash - remove all lines beginning with 'P'

Question

I have a text file that\'s about 300KB in size. I want to remove all lines from this file that begin with the letter \"P\". This is what I\'ve been using:

&g         


        

Answer 1

With awk:

awk '!/^P/' file.txt

Explanation

1. The condition starts with an ! (negation), that negates the following pattern ;
   • /^P/ means "match all lines starting with a capital P",
2. So, the pattern is negated to "ignore lines starting with a capital P".
3. Finally, it leverage awk's behavior when { … } (action block) is missing, that is to print the record validating the condition.

So, to rephrase, it ignores lines starting with a capital P and print everything else.

Note

sed is line oriented and awk column oriented. For your case you should use the first one, see Edouard Lopez's reponse.