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tutorial:linux_tutorial_four [2016/05/20 11:48] (current)
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 +=====Linux Tutorial Four=====
 +====4.1 Wildcards====
 +
 +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 directory, type
 +
 +<​code>​compsci-user@tim:​~$ ls list*</​code>​
 +
 +This will list all files in the current directory starting with **list....**
 +
 +Try typing
 +
 +<​code>​compsci-user@tim:​~$ ls *list</​code>​
 +
 +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**. ​
 +Try typing
 +
 +<​code>​compsci-user@tim:​~$ ls ?​list</​code>​
 +
 +====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====
 +
 +===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
 +
 +<​code>​compsci-user@tim:​~$ man wc</​code>​
 +
 +Alternatively
 +
 +<​code>​compsci-user@tim:​~$ whatis wc</​code>​
 +
 +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,
 +
 +<​code>​compsci-user@tim:​~$ apropos keyword</​code>​
 +
 +will give you the commands with keyword in their manual page header. For example, try typing
 +
 +<​code>​compsci-user@tim:​~$ apropos copy</​code>​
 +
 +====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  |