Usage of Wildcards

Table of Contents

• Introduction
• Wildcards
• Examples

Introduction

Shell has a fantastic feature called Wildcards, which makes bash operations more powerful when used with commands. Wildcards can be used with any commands that takes files and directories as their arguments. Such as cp, mv, rm, mkdir etc.

Wildcards

We are using a simple command called echo to explore wildcards functionality. This command just displays text. It doesn’t alter any files and folders. So it is good to check wildcard functionality with echo command before proceeding.

Examples

Example 1

me@linux ~ $ echo sample text
sample text

sample text is not the command. So it is displayed as it is. Mistyping of wildcards also displayed as it is.

me@linux ~ $ echo 2014-{01,02,03}
2014-01 2014-02 2014-03

Example 2

The {} wildcard expands 2014-{01,02,03} into 2014-01 2014-02 2014-03. Lets use this with mkdir command.

me@linux ~ $ mkdir album
me@linux ~ $ cd album
me@linux ~/album $ mkdir 2014-{01,02,03}
me@linux ~/album $ ls
2014-01  2014-02  2014-03

me@linux ~/album $ mkdir 2014-{04..12}
me@linux ~/album $ ls
2014-01  2014-03  2014-05  2014-07  2014-09  2014-11
2014-02  2014-04  2014-06  2014-08  2014-10  2014-12

Above command creates directories with given range. Here is one more command.

me@linux ~/album $ echo a{b{c,d},e{f,g}}h
abch abdh aefh aegh

Example 3

me@linux ~/album $ cd ~
me@linux ~ $ echo *
album Desktop Documents Downloads Music Pictures Public Templates Videos

Wildcard * is expanded into all files and directories in current working directory.

Example 4

To show hidden files in current working directory:

me@linux ~ $ echo .*
. .. .adobe .bash_history .bash_logout .cache .cinnamon .config
 .dbus .dmrc .gconf .gksu.lock .gnome2 .gnome2_private .ICEauthority
 .linuxmint .local .macromedia .mozilla .profile .thunderbird
 .Xauthority .xsession-errors

Example 5

For files and folders start with a particular character -

me@linux ~ $ echo D*
Desktop Documents Downloads

Above command shows files and directories starts with letter D.

To show files and directories ends with particular character:

me@linux ~ $ echo *s
Documents Downloads Pictures Templates Videos

Example 6

me@linux ~ $ echo /usr/*/share
/usr/local/share

Above command shows directory list in /usr directory which has another directory called share.

Example 7

me@linux ~ $ echo /u??
/usr

Above command shows files and directories with exactly three letters length that starts with the letter u in root directory.

Example 8

me@linux ~ $ echo /???
/bin /dev /etc /lib /mnt /opt /run /srv /sys /tmp /usr /var

Above command searches for files and directories with exactly three letters length in root directory

Example 9

me@linux ~ $ echo [DV]*
Desktop Documents Downloads Videos

This command displays all files and directories that starts with either D or V.

Example 10

me@linux ~ $ echo [[:upper:]]*
Desktop Documents Downloads Music Pictures Public Templates Videos

This command displays all files and folders that starts with Uppercase letters.

Few more patters

Here are some more patterns:

• d*.txt - Operation occurs on any text file that begins with d character
• [![:digit:]]* - Operation occurs on any file not beginning with numeral.
• *[[:lower:][:digit:]] - Operation occurs on any file that ending with either lowercase letter or numeral