UNIX Tutorial Four
The use of pattern matching (wildcards), filename conventions and built in help systems.
4.1 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 unixstuff directory, 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
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).
| 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.
4.3 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 |
