[SOLVED] Sed: can not replace part of the string whithout replacing all of it

Issue

I am trying to replace part of the string, but can not find a proper regex for sed to execute it properly.

I have a string /abc/foo/../bar And I would like to achive the following result: /abc/bar

I have tried to do it using this command:

echo $string | sed 's/\/[^:-]*\..\//\//'

But as result I am getting just /bar.

I understand that I must use group, but I just do not get it. Could you, please, help me to find out this group that could be used?

Solution

You can use

#!/bin/bash
string='/abc/foo/../bar'
sed -nE 's~^(/[^/]*)(/.*)?/\.\.(/[^/]*).*~\1\3~p' <<< "$string"

See the online demo. Details:

• -n - suppresses default line output
• E - enables POSIX ERE regex syntax
• ^ - start of string
• (/[^/]*) - Group 1: a / and then zero or more chars other than /
• (/.*)? - an optional group 2: a / and then any text
• /\.\. - a /.. fixed string
• (/[^/]*) - Group 3: a / and then zero or more chars other than /
• .* - the rest of the string.
• \1\3 replaces the match with Group 1 and 3 values concatenated
• p only prints the result of successful substitution.

Answered By - Wiktor Stribiżew

Answer Checked By - Candace Johnson (WPSolving Volunteer)