Wildcards and 'globbing'

Globs are wildcard patterns that let the command-line match multiple files at once. The most useful wildcard is *, which means 'match anything'. For example this command:

% ls *.txt

will list all files ending in '.txt' in the current directory.

A glob can have multiple '*' characters in it - e.g. to get a list of files that have 'file' in the name and end in '.txt':

% ls *file*.txt

This feature can be combined with any command that uses a file, and is quite powerful.

To illustrate this, here is a command sequence that creates a new temporary folder, copies all text files into it, removes listing.txt, concatenates all the others into one big text file, and then removes the temporary files:

% mkdir tmp_folder
% cp *.txt tmp_folder/
% rm tmp_folder/listing.txt
% cat tmp_folder/*.txt > concatenated.txt
% rm tmp_folder/*.txt
% rmdir tmp_folder

Note

Depending on your shell, you might find that pressing <tab> before <enter> has the effect of expanding the wildcard, right there on your terminal. This is what is happening under the hood: *.txt is shorthand for typing out all the files that would match *.txt, one by one, on the command line.

Apart from *, which is the most useful glob special character, there are a few others as well. But '*' is the most useful.