Chris Tyler - Fedora Linux

When bash receives a command, it splits it into words and uses globbing to expand any ambiguous filenames. bash next checks to see if the first word is a built-in command. If not, it treats it as an external command or program and searches a list of directories to find that program. It executes that program, passing the other words to the program as arguments. Almost all Linux commands are external programs.

Linux commands generally accept three types of arguments:

Options

These start with a hyphen or double-hyphen ( - or -- ) and modify the way the command operates. For example, the ls (list-files) command will include hidden files in its output if the -a argument is given, and will list detailed information about files when the -l option is specified. These options may be used individually, used together in any order, or combined after one hyphen if they all use a single hyphen:

$ ls -l

$ ls -a

$ ls -l -a

$ ls -a -l

$ ls -al

$ ls -la

Positional arguments

These have significance according to the order in which they are specified. For example, the cp (copy) command accepts two or more filenames:

$ cp one two

one is the name of the file being copied, and two is the name that will be given to the new copy. If you swap the position of the two arguments, the meaning of the command is changed. Options may be placed before, between, or after positional arguments; usually, the positions of the options don't matter.

Options with a value

These combine options with positional arguments. An option with a value may be placed before or after other arguments, but the value must be placed directly after the option.

For example, the ls command accepts the -w option (width of output), which is specified along with a number indicating the desired width of output in characters. This can be combined with the -a and -l options in any order, as long as the number immediately follows the -w option:

$ ls -a -l -w 60

$ ls -w 60 -al

$ ls -l -w 60 -a

$ ls -l -w60 -a

$ ls -alw60

Fedora is configured to allow you to log in using a character-mode display even if the graphical user interface is running. In fact, you can log in up to six times, using the same or different user IDs.

The key is Virtual Terminals (VTs). There are 12 virtual terminals that can be accessed easily: VT1 through VT6 are configured for character-mode login, VT7 is used for graphical login, and VT8 through VT12 are not normally used.

To switch to a specific VT, press Ctrl-Alt and the function key that corresponds to the virtual terminal you wish to access (Ctrl-Alt-F1 for VT1, Ctrl-Alt-F7 for VT7, etc.).

There are actually 64 virtual terminals, but virtual terminals above number 12 are not directly accessible from the keyboard and are therefore rarely used.

You can log in on multiple VTs simultaneously and switch back and forth between them. This is particularly useful when you bring up documentation on one VT and enter commands on another.

The type , which , and whereis commands all provide information about the location of programs.

type will tell you where a command is located in a verbose way, along with an indication of whether the command location is hashed (stored in the shell for quick reference because the command has already been used recently). If there is more than one command with the same name, the location shown is the first one found using your $PATH :

$ type cat

cat is hashed (/bin/cat)

which is similar, but shows only the command location:

$ which cat

/bin/cat

whereis will show you all of the locations for the command (and sometimes there are several, if different versions of the same program are installed), along with the location of its manpage documentation:

$ whereis cat

cat: /bin/cat /usr/share/man/man1p/cat.1p.gz /usr/share/man/man1/cat.1.gz

Programs with a graphical user interface are started in exactly the same way as programs with a character-based user interface. GUI-based programs use the DISPLAY environment variable to determine if a graphical display is available and to connect to that display. Some programs, such as system-config-printer , will automatically start up with a graphical or a character-based user interface according to the type of display that is available.

Typing Alt-F2 will open a Run Application dialog (in KDE, it's called Run Command), which enables you to enter a single command and run it. This is most useful for starting graphical programs that aren't on the menu.

You can also add an applet to your panel bar that does the same thing.

There isn't any! Linux does not make any distinction between categories of programs.

Fedora offers four different command shells: csh (a.k.a. tcsh ), bash (a.k.a. sh ), ksh , and zsh . You can temporarily start a different shell just by typing the shell name:

$ csh

Press Ctrl-D or type exitto return to the original shell. You can permanently change your default shell using the chsh (change shell) command:

$ chsh

Password:

bigsecret

New shell [/bin/bash]:

/bin/csh

Shell changed.

The password requested is your normal login password; the change will take effect the next time you log in.

chsh requires that you enter the full pathname of the new shell. To see a list of available shells, use chsh with the -l (list) option:

$ chsh -l

/bin/sh

/bin/bash

/sbin/nologin

/bin/ksh

/bin/tcsh

/bin/csh

/bin/zsh

zsh , ksh , and bash each use a syntax related to the original Bourne shell ( sh ). csh uses a very different syntax, which C programmers often find comfortable.

 The bash , chsh , csh , zsh , and ash manpages

A fully loaded Fedora system includes over 4,700 programs, plus programming interfaces, data files, and graphical tools. To help you learn your way around, over 12,000 files of online documentation are available, with additional documentation available through the Web. Knowing how to access and knowledgeably navigate through this documentation is essential to getting the most out of your Fedora system.