By compressing files and directories into a compressed file, we can easily move and back up the compressed file.

Packaging and Compressing Files

Before we start selecting tools, we need to compare the pros and cons of each compression tool, so let’s do it. We should take into account the feelings of these people. We need to get their consent before we can interview them.

Let’s prepare a file:

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dd if=/dev/zero of=100MBFile bs=102400 count=1

Packaging with tar

The tar command is a standard compression and decompression tool.

The suffix of the tar file is .tar

Here are some options provided by the tar command:

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# Create a general archive, this won't lessen the size
tar -cvf 100MBFile.tar 100MBFile    # In addition to f, other options' position can be changed at will
ll 100MB*

Compressing with -z option

By adding the z option, the tar command compresses the file with the gzip algorithm:

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tar -czvf 100MBFile.tar.gz 100MBFile
ll 100MB*

Compressing with gzip

Since gzip will delete the original file after compression, we need to clone a new file:

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# Clone 100MBFile to 100MBFileGZIP
cp 100MBFile 100MBFileGZIP
ll 100MBFile*

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# This will use the Lempel-Ziv coding (LZ77) to compress the file
gzip 100MBFileGZIP
ll 100MBFile*

Compressing with bzip2

An upgraded version of gzip.

Since bzip2 will delete the original file after compression, we need to clone a new file:

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# Clone 100MBFile to 100MBFileGZIP
cp 100MBFile 100MBFileBZIP2
ll 100MBFile*

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# This will use the Burrows-Wheeler block sorting text compression algorithm and Huffman coding to compress the file
bzip2 100MBFileBZIP2
ll 100MBFile*

Compressing with xz

A tool with a high compression ratio.

Since xz will delete the original file after compression, we need to clone a new file:

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# Clone 100MBFile to 100MBFileXZ
cp 100MBFile 100MBFileXZ
ll 100MBFile*

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xz 100MBFileXZ
ll 100MBFile*

Unpackaging and Decompressing Files

Unpackaging with tar

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tar -xf 100MBFile.tar    # tar command will keep the archived file after decompressing
ll 100MBFile*

Decompressing with gunzip

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gunzip 100MBFileGZIP.gz    # gunzip command will remove the archived file after decompressing
ll 100MBFile*

Decompressing with bunzip2

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bunzip2 100MBFileBZIP2.bz2    # bunzip2 command will remove the archived file after decompressing
ll 100MBFile*

Decompressing with unxz

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unxz 100MBFileXZ.xz    # unxz command will remove the archived file after decompressing
ll 100MBFile*

View Packed Files and Compressed Files Contents

Let’s prepare some text files that can be viewed in a compressed file:

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echo 'This is a README.txt file for GZIP' > READMEGZIP
echo 'This is a README.txt file for BZIP2' > READMEBZIP2
echo 'This is a README.txt file for XZ' > READMEXZ
gzip READMEGZIP
bzip2 READMEBZIP2
xz READMEXZ
ll README*

Viewing Files with tar

List option for tar command:

We can view the files packed in the .tar archive with option -t:

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tar -tf 100MBFile.tar    # Don't forget the f option behind it

Viewing Files with gzip

List option for gzip command:

We can view the files compressed in the .gz archive with option -l or –list:

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gzip -l READMEGZIP.gz    # This is equivalent to gzip --list READMEGZIP.gz

Viewing Files with xz

List option for xz command:

We can view the files compressed in the .xz archive with option -l or –list:

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xz -l READMEXZ.xz    # This is equivalent to xz --list READMEXZ.xz

Viewing with zcat, zmore, bzless, zgrep

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zcat READMEGZIP.gz
zmore READMEGZIP.gz
zgrep -e 'is a' READMEGZIP.gz

zless will be another option.

Viewing with bzcat, bzmore, bzless, bzgrep

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bzcat READMEBZIP2.bz2
bzmore READMEBZIP2.bz2
bzgrep -e 'is a' READMEBZIP2.bz2

bzless will be another option.

Viewing with xzcat, xzmore, xzless, xzgrep

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xzcat READMEXZ.xz
xzmore READMEXZ.xz
xzgrep -e 'is a' READMEXZ.xz

xzless will be another option.

References 11.2 dd: Convert and copy a file, GNU tar: an archiver tool, GNU Gzip, bzip2 Documentation, XZ Utils

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