CODEWITHSUNDEEP
linuxbashunixsedcomments
chipunpui
chipunpui

Reputation: 11

Unix/Linux, Delete comments from lines

I need to delete/remove comments from a user-input line without deleting any codes. So for example:

mail -s 'text' brown < text #comments

How do I remove the comments and leave the code intact? I can delete lines that begin with #, but not if it begins somewhere in the middle of the lines.

I tried:

echo $line | sed -e 's/\

but it does not work. Any idea what I'm doing wrong?

Also, how to detect cases in which # is not used to begin a comment? For example quoted # and line of code that ends with # since they are not comments.

echo $line | sed -e  '/^#/d'

In this line, the # is not used as a comment, but as part of code. I figure out that I need to detect that if # is within quotes or does not have a whitespace character before the #. How do I leave the output as it is?

Upvotes: 1

Views: 2079

Answers (2)

Jotne
Jotne

Reputation: 41446

You can remove all from # to end of line using this awk

awk '{sub(/#.*$/,"")}1' file

But if you have file like this:

#!/bin/bash
pidof tail #See if tail is running
if [ $? -ne 0 ] ; then  #start loop
   awk '{print " # "$8}' file >tmp # this is my code
fi # end of loop
awk -F# '{for (i=1;i<=NF;i++) print $i}' file > tmp2
a=a+1 # increment a

There are no way you can remove the comment automatically without destroying some.

Upvotes: 3

RICK
RICK

Reputation: 273

Well, consider what almost always comes after a comment in bash.

#comment...
#another comment

A line break! Which is effectively a character. So, all you have to do is add a wildcard after your #, to include the actual comment text, then put a line break 'character' at the end. You'll actually need to use \n rather than trying to hit Enter. Unfortunately I'm not on linux at the moment, and sometimes delimiters (the backslash) don't work properly. Trying something like `\n` might work, or maybe using $'\n'.

EDIT: With regex ^ will indicate the start of a new line, while $ indicates the end.

As for not deleting actual code, matching for a space immediately followed by # should work. I would match for a space OR line break preceding the #.

At any rate, please be sure not to accidentally ruin whatever you're working on, just in case I'm wrong.

Upvotes: 0

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