Viewing compressed file content on Linux without uncompressing

If you need to check the contents of a compressed text file on Linux, you don’t have to uncompress it first. Instead, you can use a zcat or bzcat command to extract and display file contents while leaving the file intact. The “cat” in each command name tells you that the command’s purpose is to display content. The “z” tells you that it works with compressed files.

Which of the two commands to use depends on the type of compressed file you are examining. If the file was compressed with gzip or zip, you would use the zcat command. If the file was compressed with bzip2, you would use the bzcat command. On some systems, zcat might be called gzcat.

You can identify the command used to compress a file by the compressed file’s extension.

• .gz or .tgz = gzipped files, use zcat (or gzcat)
• .zip = zipped files, use zcat (or gzcat)
• .bz2 = bzipped files, use bzcat

In the example below, the top 20 lines of H. G. Wells’ “The War of the Worlds” is displayed from a file compressed with bzip2.

$ bzcat The_War.bz2 | head -20
No one would have believed in the last years of the nineteenth century
that this world was being watched keenly and closely by intelligences
greater than man’s and yet as mortal as his own; that as men busied
themselves about their various concerns they were scrutinised and
studied, perhaps almost as narrowly as a man with a microscope might
scrutinise the transient creatures that swarm and multiply in a drop of
water. With infinite complacency men went to and fro over this globe
about their little affairs, serene in their assurance of their empire
over matter. It is possible that the infusoria under the microscope do
the same. No one gave a thought to the older worlds of space as sources
of human danger, or thought of them only to dismiss the idea of life
upon them as impossible or improbable. It is curious to recall some of
the mental habits of those departed days. At most terrestrial men
fancied there might be other men upon Mars, perhaps inferior to
themselves and ready to welcome a missionary enterprise. Yet across the
gulf of space, minds that are to our minds as ours are to those of the
beasts that perish, intellects vast and cool and unsympathetic,
regarded this earth with envious eyes, and slowly and surely drew their
plans against us. And early in the twentieth century came the great
disillusionment.

To display only a portion of the text, pass the command output to another command like the head command shown above or to a grep command that includes the text you are searching for. For example:

$ bzcat The_War.bz2 | grep vastness
Haggerston and Hoxton, and, indeed, through all the vastness of London
throughout the inanimate vastness of sidereal space. But that is a

After the bzcat display, the file remains compressed.