article deals with 2 issues which are many a times used with
each other. The first one is about wildcards and the other one
is the use of special characters while typing commands at the
I call this a Special Guide since the information in this
article helps you with many of your commands and is not restricted
to any particular application as such. Thus reading this article
is a must for all Linux users.
In Linux whenever you are not sure about the name of a file
and you want to do something with files such as either search
for them or copy them or delete some files based on some knowledge
you have about the filenames then you can use Wildcards. Wildcards
are basically an indicator to the shell that some particular
part of the filename is not known to you and the shell can insert
a combination of characters in those places and then work on
all the newly formed filenames. This concept would be clear
by the end of this article
There are 3 types of wildcards that can be used Linux. They
are the * ? and  . All the 3 shall be explained in detail.
This represents any sequence of characters. This means that
if you include a * in your filename then that part of the filename
can be formed using any sequence of characters. The example
below explains this concept
$ cat article* > combinedarticle
Would find all the files that begin with the letter sequence
' article ' and can have anything following those letters. I
mean article01 or article10 or articlenew.. and any such file
would be considered. All these files would be merged and would
be written to a file named combinedarticle
$ ls *gif
Would list all the files having the letters ' gif ' in them.
So a file named somegifs.txt as well as a file named 123.gif
would be listed in the output.
$ ls *.gif
Would list all the files having ' gif ' as the extension of
their filename. Thus in this case a file named somegifs.txt
file would NOT be listed since its extension is not '
gif '. Whereas a file named 123.gif would be listed.
$ ls *day*
Would list all the files that have the letters ' day ' anywhere
in their filenames. Thus files such as today.txt , dayone.txt
and lastday.gif would all be listed in the output.
$ ls .*gif*
Would list all the hidden files in the current directory that
have the letters ' gif ' in their filenames. Hidden files in
Linux begin with a . (period) in their filenames.
$ pl * a.txt
Notice that there is a space between the * and ' a.txt ' . It
is this space that causes the command to act as if 2 parameters
have been passed to ' pl ' rather than one. The above
command would print all the files that are present in the current
directory. Once that is done it would proceed to the next file
named a.txt and would print that also if it exists.
Note : The * would not work with the ' . ' (period) that
exists in filenames. Thus in case you use ' *a ' and there is
a file whose name begins with ' .a ' , it would not be listed.
When a . (period) is the first character in a filename then
the file becomes a hidden file in Linux.
? (Question Mark) Wildcard
This represents only one character which can be any character.
Thus in case you know a part of a filename but not one letter,
then you could use this wildcard. If there are many files that
are named such as article10, article11 and so on till article19
you could get all these files by using article1? . In this case
the ? would be interpreted as any one character and it would
find all the files like article10, article11..and so on till
article19, since all these files differ in their names by only
the last letter.
$ ls article1?
Would list all the files that begin with ' article1 ' and have
one more character in their names which can be any one valid
$ ls ??.gif
Would list all the .gif files in the current directory that
have only 2 characters before the extension. Thus files such
as ab.gif or xy.gif would be listed but 123.gif would not be
Remember that the ? means any ONE character to be substituted
in the place of the ?
$ ls *.???
Would list all the files in the current directory that have
a file extension of 3 characters in length. Thus files having
extensions such as .gif , .jpg , .txt would be listed.
(Square Brackets) Wildcard
This represents a range of characters. So in case you have files
that are named article10, article11, article12..all the way
till article19 then you could select all the first 5 of them
using the above wildcard as shown below
$ ls article1[0-4]
Remember that  represents a range from which any character
can be present. This range can be something like [0-4] or [1-9]
or anything like that in case of numbers. Letters could also
be selected such as [a-g] or [F-Z] or [A-Z].
Note : Remember that in Linux the filenames are case
sensitive, Thus a range of [a-z] is different from [A-Z]
Would list all the files that begin with the letter sequence
' beckham ' and end with either a 1, 2 or 3. Thus the possible
filenames that could be listed (if they exists) are beckham1.jpg
, beckham2.jpg and beckham3.jpg
$ ls [a-d,A-D]*.jpg
This would list all the files that have an extension as .jpg
and have as their first letter either a,b,c,d,A,B,C or D . The
[ , ] imply that this entire range indicates ONLY ONE
letter which can be from any of the two given sub-ranges. A
comma is used to merge different range of letters or numbers.
Note : I would once again like to mention that [a-d,p-z] does
NOT mean that there can be two letters, the first one
from a to d and the second one from p to z. It means that there
is ONLY ONE letter, and that letter can be from either
a to d or from p to z.
In case you want to specify the range for 2 characters in the
filenames then use the following as follows
$ ls beckham[0-9][0-9]
Read the second part of this article to know about the use of
special characters such as quotes and apostrophe marks.
Goto Page 2 of this article