Hi,
I need to convert user-input from '(this)' to '\(this\)' before passing it to egrep. I've tried using TR, SED and NAWK to add the backslash, but the most I ever get is a backslash without a '(' or ')'.

Any ideas?

Thanks!

why not put the user input into a variable then just add your sting like


egrep \"${user_input}"\ filename_to_search

My goal is to insert the backslashes within the user's search string. If I understand your suggestion, the backslashes would surround the entire search string.

Notice that when I converted '(this)' to '\(this\)', the last parenthesis is preceded by a backslash.

The user's search string could easily be something like this as well: '12.1(3)T', so that the parenthesis are completely within the search string.

I hope I didn't misunderstand your suggestion.

sed 's/\([()]\)/\\\1/g'

For some reason that I can't determine, this works only from a command line, not from within the script. When run from a script, my search string (which I'm echoing so I can see the conversion) looks like this:
search string: '(this)'
output: \1this\1

From the script:
search_arg=`echo "$*" | tr -s ' '` #remove redundant spaces
search_arg=`echo "$search_arg" | sed 's/\([(.)]\)/\\\1/g'`
echo "$search_arg"

This is the trouble with backslashed backslashes...you need more of them each time they get evaluated. And what's with that dot? I didn't have that. I took it back out.

Try:
search_arg=`echo "$search_arg" | sed 's/\([()]\)/\\\\\1/g'`

Perfect! Thanks very much!

The dot was my addition...I also want a slash in front of periods, so that they don't act as single-character wildcards.

Here's the final product:
search_arg=`echo "$*" | tr -s ' ' | sed 's/\([(.)]\)/\\\\\1/g'`