Reading Compressed Files With less

Juliet Kemp
less, the better-featured version of more, which among other things allows you to move backward through its output, is great for paging through text files. But it won't automatically deal with compressed text files. This can be a nuisance, particularly when many of the files in /usr/share/doc are gzipped.

Tip of the Trade: Sometimes, less really is more. In the case of the app less, it is also the better-featured version of its bigger sibling, more.

A straightforward alternative is zless, which will deal seamlessly with gzip, compress, or pack files, allowing you to page through them without having to unzip them. It also handles uncompressed files, and (contrary to the manpage) it appears to deal OK with input piped from stdin (e.g., ls | zless).

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zless can't, however, handle files that have been tarred as well as zipped. Here's an alternative command line that will allow you to page through file.tar.gz without unpacking it beforehand and thus without leaving unzipped files lying around:

tar --to-stdout -zxf file.tar.gz | less
That's great, but it's a bit of a mouthful (or keyboardful) to remember. Try this instead (bash syntax):
export LESSOPEN="|tar --to-stdout -zxf %s"
Now try just typing less file.tar.gz. Magic!

In fact, this will deal with both uncompressed files and piped input as well, so you can set this variable in your .bashrc. However, it won't work on plain .gz files – for those, you should still use zless.

One last note: If you regularly want to look at tar archives that aren't also zipped (e.g., file.tar), you can set export LESSOPEN="|tar --to-stdout -xf %s" to work the same trick for these files.

This article was originally published on Jan 26, 2009
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