Remove and replace characters from string with one command

Question

I need to remove characters from string and then replace other characters. This is the initial string:

something/filename.txt

I need to remove the directory "something" (can be any other name) and replace .txt with .gz The following 2 commmands work perfect:

newfile=${newfile#*/}
newfile=${newfile::-4}.gz

So the output will be: filename.gz Is there a way to do it in a single command? Something like:

${${$newfile#*/}::-4}.gz

With the above command I get: bad substitution error.

Thank you Lucas

You get a bad substitution because Parameter Expansions works on parameters (variables), e.g. ${param#*/} and ${param::-4}. In ${${newfile#*/}::-4}.gz , ${newfile#*/} is NOT a parameter. Use 2 parameter expansions and don't worry about combining them. — David C. Rankin
– David C. Rankin, Commented Oct 5, 2021 at 5:30

jared_mamrot · Accepted Answer · 2021-10-05 05:58:59Z

2

Perhaps you could use basename, i.e.

name_of_file="something/filename.txt"
newfile=$(basename "${name_of_file%%.*}".gz)
echo "$newfile"
filename.gz

answered Oct 5, 2021 at 5:58

jared_mamrot

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Léa Gris · Accepted Answer · 2021-10-05 07:09:04Z

2

Since your question is tagged bash, you can use Bash builtin regex to capture the group you need like this:

#!/usr/bin/env bash

filepath=something/filename.txt

# Regex group capture basename without dot suffix || exit err if not matching
[[ $filepath =~ .*/(.*)\.[^.]* ]] || exit

# Compose new file name from Regex captured group and new .gz extension
newfilename=${BASH_REMATCH[1]}.gz

# debug dump variables
declare -p filepath newfilename

edited Oct 5, 2021 at 7:09

answered Oct 5, 2021 at 6:29

Léa Gris

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Jetchisel · Accepted Answer · 2021-10-05 06:08:48Z

1

new_file=something/filename.txt
new_file="${new_file#*/}"
new_file="${new_file%.*}.gz"

Is there a way to do it in a single command?

echo something/filename.txt | sed 's|.*/||;s|\..*$|.gz|'

answered Oct 5, 2021 at 6:08

Jetchisel

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BigHeadNelson · Accepted Answer · 2021-10-05 06:28:32Z

0

A combination of cut and sed can help as below

oldfile='somethingelse/filename.txt'
newfile=`echo $oldfile | cut -d "/" -f2 |sed 's!.txt!.gz!g'`
echo $newfile

This displays filename.gz

EDIT In case there are subdirectories and you want only file name

oldfile='somethingelse/other/filename.txt'
newfile=`echo $oldfile | rev| cut -d "/" -f1 |rev |sed 's!.txt!.gz!g'`
echo $newfile

The cut command gets the last field delimited by "/" .

Happy to be corrected and learn.

edited Oct 5, 2021 at 6:28

answered Oct 5, 2021 at 6:22

BigHeadNelson

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