In order to access a UNIX system, and use it , you need to connect to the system. You can login:
Locally
Remotely
Login Types In general, there are two ways:
Command-line Login
GUI Login
Connecting Locally Connecting locally means, you are directly logging into the UNIX system. Network connectivity is not required.
You could login using the command-line or a GUI interface depending on the system configuration. Example of a GUI login interface on a CentOS machine
User enters "username" on this screen and hits enter.
User enters the password on this scree and hits "Sign In"
Example of a command line login interface (Unix System with no GUI interface) login as: mususer1 password: Note
You could have GUI interface installed, and force the command-line login as default.
Connecting Remotely To
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External Commands Examples:
grep sort uniq
Listing all shell built-in commands - "help" command
Bash shell has a command called "help".
Just type "help", and hit enter.... it will display all the built-in commands.
How do you determine if a given command is an internal or external?
You can use one of the following:
which command type command
Searching all over the filesystem. (... not a preferred way. Instead use type or which)
We will use "type" command to determine about the "grep" and "cd" commands:
For external commands, the command displays the physical path.
For internal commands, the messages indicated that it is a builtin command.
$ type grep find is /usr/bin/grep
$
$ type cd cd is a shell builtin
$
We will use "which" command to determine about the "grep" and "cd" commands:
For external commands, the command displays the physical path.
For internal commands, there would be no response.
$ which grep
/bin/grep
$
$ which cd
$
Internal commands are much faster than external commands, as there is no process to spawn.
Well.... you don 't have an internal command for every external