Decompress and print files with bzcat command in Linux terminal

In this tutorial, we will learn about another Linux/Unix command line tool, bzcat. It is used compress and decompress files using the Burrows-Wheeler block sorting text compression algorithm, and Huffman coding. The command-line options are deliberately very similar to those of GNU gzip, but they are not identical.

How to install bzcat tool?

Debian based - apt install bzip2
Raspbian - apt-get install bzip2
Alpine - apk add bzip2
Arch Linux - pacman -S bzip2
CentOS - yum install bzip2
Fedora - dnf install bzip2
OS X - brew install bzip2
Docker - docker run cmd.cat/bzip2 bzip2

More about bzcat command

bzcat expects a list of file (which are compressed) names to accompany the command-line flags/options. Each file is replaced by a decompressed version of itself. Each compressed file has the same modification date, permissions, and, when possible, ownership as the corresponding original, so that these properties can be correctly restored at decompression time. File name handling is naive in the sense that there is no mechanism for preserving original file names, permissions, ownerships or dates in file systems which lack these concepts, or have serious file name length restrictions, such as MS-DOS systems.

Files which were not created by bzcat will be detected and ignored (based on hex values), and a warning issued. bzcat attempts to guess the filename for the decompressed file from that of the compressed file as follows:

filename.bz2 becomes filename
filename.bz becomes filename
filename.tbz2 becomes filename.tar
filename.tbz becomes filename.tar
anyothername becomes anyothername.out

Notice that if the provided compressed file does not have a file extension (bz2,bz.tbz.tbz2) then the compressed file will get ".out" appended to the original name.

Syntax of bzcat command:

bzcat [ -s ] [ filenames ...  ]
bzcat [ -h|--help ]

Options of bzcat command:

bzcat command example

We will use this file for further examples:

$ echo -e "This is a file containing plain text. \nWe will use this text file for bzip commands explanation" > foo
$
$ cat foo
This is a file containing plain text.
We will use this text file for bzcat commands explanation

1. Decompress data with bzcat command

One of the most straightforward use cases of the bzcat command is to decompress the provided data and write it to a file. Let’s take a look at the two ways to do so:
Read data from a file and write a decompressed form of that data to the same file and also remove .bz2 as extension. i.e, The file named foo.bz2 becomes foo after decompression.

$ ls
foo.bz2
$ bzcat foo
$ ls
foo

Read data from standard input (stdin) and decompress the data. So, let us again use bzcat to decompress data for a file named bar.

$ cat bar | bzcat
bzcat: I won't read compressed data from a terminal.
bzcat: For help, type: `bzcat --help'.

But, If no file names are specified, bzcat decompresses from standard input to standard output. In this case, bzcat will decline to write decompressed output to a terminal.

$ cat bar | bzcat > foo
$ ls
bar  foo
$ cat -A foo
This is a file containing plain text. \nWe will use this text file for bzcat commands explanation

Use -dc (or -d -c) options to read data from a file and decompress the data and write to standard output.

$ bzcat -zc foo.bz2 > foo
$ ls
foo  foo.bz2

2. Compress data using bzcat command

Read data from a file and write a compressed form of that data to the same file and also add .bz2 as extension. i.e, The file named foo becomes foo.bz2 after compression.

$ ls
foo
$ bzcat -c foo
$ ls
foo.bz2

Read data from standard input (stdin) and compress the data. So, let us again use bzcat to compress data for a file named foo.

$ echo -e "This is a file containing plain text. \nWe will use this text file for bzcat commands explanation" | bzcat -c
bzcat: I won't write compressed data to a terminal.
bzcat: For help, type: `bzcat --help'.

But, If no file names are specified, bzcat (with -z option) compresses from standard input to standard output. In this case, bzcat will decline to write compressed output to a terminal, as this would be entirely incomprehensible and therefore pointless.

$ echo -e "This is a file containing plain text. \nWe will use this text file for bzip commands explanation" | bzcat > bar
$ ls
bar  foo
$ cat -A bar
BZh91AY&SYM-QM-^KM-^?V^@^@^IM-SM-^@^@^P@^A^DM-^@?M-gM-^M-P ^@@M-SM"OSM-TM-rM-^^M-!M-dOBM-^@^@^C&F^]g9M-2M-sM-$M-0hM-?^YTV^QM-LM-aM-^J^\^&^KJM-kM-hM-jM-R1M->4+M-^AM-K_M-M-t^D?.lM-tM-\M-^WM-r7^CM-\M-ZM-^DiM-7M-XM-;M-^R)M-BM-^DM-^FM-^L_M-zM-0

Use -zc (or -z -c) options to read data from a file and compress the data and write to standard output.

$ bzcat -zc foo > foo.bz2
$ ls
foo  foo.bz2

Conclusion

In summary, the Linux bzcat command is a useful tool for decompressing and displaying the contents of a bzip2 compressed file. It can be used to quickly view the contents of a compressed file, or to pipe the decompressed output to other command line utilities for further processing.