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How wildcards work in Linux and Unix


Wildcards

The * wildcard

The character * is called a wildcard, and will match against none or more character(s) in a file (or directory) name. For example, in your unixstuffdirectory, type
% ls list*
This will list all files in the current directory starting with list....
Try typing
% ls *list
This will list all files in the current directory ending with ....list

The ? wildcard

The character ? will match exactly one character.

So ?ouse will match files like house and mouse, but not grouse. 
Try typing

% ls ?list

 Filename conventions

We should note here that a directory is merely a special type of file. So the rules and conventions for naming files apply also to directories.
In naming files, characters with special meanings such as / * & % , should be avoided. Also, avoid using spaces within names. The safest way to name a file is to use only alphanumeric characters, that is, letters and numbers, together with _ (underscore) and . (dot).
Good filenames
Bad filenames
project.txt
project
my_big_program.c
my big program.c
fred_dave.doc
fred & dave.doc
File names conventionally start with a lower-case letter, and may end with a dot followed by a group of letters indicating the contents of the file. For example, all files consisting of C code may be named with the ending .c, for example, prog1.c . Then in order to list all files containing C code in your home directory, you need only type ls *.c in that directory.

 Getting Help

On-line Manuals

There are on-line manuals which gives information about most commands. The manual pages tell you which options a particular command can take, and how each option modifies the behaviour of the command. Type man command to read the manual page for a particular command.
For example, to find out more about the wc (word count) command, type
% man wc
Alternatively
% whatis wc
gives a one-line description of the command, but omits any information about options etc.

Apropos

When you are not sure of the exact name of a command,
% apropos keyword
will give you the commands with keyword in their manual page header. For example, try typing
% apropos copy

Summary


Command
Meaning
*
match any number of characters
?
match one character
man command
read the online manual page for a command
whatis command
brief description of a command
apropos keyword
match commands with keyword in their man pages



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