UNIX Tutorial Four
The characters * and ?
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 unixstuff
% ls list*
This will list all files in the current directory starting with list….
% ls *list
This will list all files in the current directory ending with ….list
The character ? will match exactly one character.
So ls ?ouse will match files like house and mouse,
but not grouse.
% ls ?list
4.2 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).
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.
Beware: some applications give the same name
to all the output files they generate.
For example, some compilers, unless given the appropriate option, produce compiled
files named a.out. Should you forget to use that option, you
are advised to rename the compiled file immediately, otherwise the next such
file will overwrite it and it will be lost.
4.3 Getting Help
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,
% man wc
% whatis wc
gives a one-line description of the command, but omits any information about
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,
% apropos copy
||match any number of characters|
||match one character|
||read the online manual page for a command|
||brief description of a command|
||match commands with keyword in their man pages|
M.Stonebank@surrey.ac.uk, © 9th October 2000