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Painless file extraction on Linux


Extracting files from archives in Linux systems is considerably less painful than tooth extraction, but sometimes seems more complicated. In this post, we will take a look at how you can easily extract files from just about any kind of archive you’re likely to run into on a Linux system.

There’s a pile of them – everything from .gz to .tbz2 files with some variations for how those files are named. Sure, you can memorize all of the various commands available for extracting files from archives along with the options they offer, but you can also just deposit all that know-how into a script and stop worrying about the details.

In this post, we assemble a series of extraction commands into a script that calls the proper command to extract the content of file archives depending on the archive file names. The script starts with some commands to verify that a file name has been provided as an argument or ask that the person running the script provide one.

#!/bin/bash

if [ $# -eq 0 ]; then
    echo -n "filename> "
    read filename
else
    filename=$1
fi

if [ ! -f "$filename" ]; then
    echo "No such file: $filename"
    exit $?
fi

Got that? The script prompts for a file name if no arguments were offered and uses the argument provided if there is one. It then verifies that the file actually exists. If not, the script exits.

The next step is to use a bash case statement to call the appropriate extraction command for the archive depending on its name. For some of these file types (e.g., .bz2), other commands than tar would also work, but we only include one extraction command for each file naming convention. So, here’s the case statement with the various archive file names.

 case $filename in
    *.tar)      tar xf $filename;;
    *.tar.bz2)  tar xjf $filename;;
    *.tbz)      tar xjf $filename;;
    *.tbz2)     tar xjf $filename;;
    *.tgz)      tar xzf $filename;;
    *.tar.gz)   tar xzf $filename;;
    *.gz)       gunzip $filename;;
    *.bz2)      bunzip2 $filename;;
    *.zip)      unzip $filename;;
    *.Z)        uncompress $filename;;
    *)          echo "No extract option for $filename"
esac

If the file provided to the script has a file extension that doesn’t match any of those known to the script, the “No extract option for $filename” message will be issued. If any archive types that you use are missing, just add them along with the required extraction commands.

Copyright © 2020 IDG Communications, Inc.

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