Links In Linux
To give a pointer to the source file called a link.
In Unix/Linux two types of links.
- Soft links
- Hard links.
The inode number of the source file, link file are different.
- It can be created across the file system.
- Editing of the original file will be replicated in the link files.
- The size of the soft link file equals the number of characters in the original file path.
- If the source file is deleted the link file will not be accessible.
- It is also be called a shortcut link
Syn: $ ln-s<source file> <link file>
Ex: $ ln-s/backup/linux /root/desktop/linux
à Source file, link file has same inode numbers.
- It can’t be created across the file system.
- Editing of the original file will replicate in the link files.
- The size of the hard link file is the same as the original file.
- The source file is deleted the link file we can access.
- It is a backup link.
Syn: $/n<source file><link file>
Ex: $ /n/root/ backup/root/ desktop/ backup
*Shell concept: Shell is a command-line interpreter. The shell access request from the user and the checks command existence, if the command exists then it converts into kernel understandable language (Machine language) and it sends the given request to kernel.
The shell access interface b/w user and kernel
Inclined to build a profession as Linux Developer? Then here is the blog post on, explore Linux Training
Types of shells
|Shell name||Developed By||Prompt||Interpreter name|
|Bourne shell||Stephen Bourne||$||sh|
|Korn Shell||David korn||$||ksh|
|C shell||Bill joy||%||csh|
|Bash shell||Stephen Bourne||$||bash|
|Z shell||paul||$||z sh|
Note: The advanced version of the Bourne shell is the bash shell.
- Bash means “Bourne again shell”
- Bash shell is the default in Linux.
Default shell name Flavour name
Bash Shell Linux
Bourne Shell SCo_Unix, Solaris, HP_UX
Korn Shell IBM_AIX
C shell IRIX (Silicon Graphics)
|Default shell name||Flavour name|
|Bourne Shell||SCo_Unix, Solaris, HP_UX|
|C shell||IRIX (Silicon Graphics)|
Features of shells
- Word completion
- Command History.
- Command alias.
To check the shells:
#cat / etc/shells
To check the parent shell of the current user:
# echo $ SHELL
To view the available shells:
#Cd /bin #ls * sh
To shift from bash shell to sh shell:
To shift from sh shell to k shell:
To check the current working shell:
To exit the shell:
Linux automatic command completion is a tool or program that can identify what you are typing in the Linux command line terminal and can complete that command, words, or sentence for you. This is really cool feature in Linux
- When the <TAB> key is pressed, any command starting with the given string will be completed by the system automatically.
- For multiple commands that starting with the given string, pressing the <TAB> key twice will list down all those matched files or commands.
- If there are no match of any command, files, or folders, then, the automatic word completion will not show, a ‘ting’ sound will buzz.
Ex: $cd /var/l<tab>Lib/lock/ log/
The history command performs one of several operations related to recently – executed commands recorded in a history list. Each of these recorded commands is referred to as an ‘event’, when specifying an event to the history command.
$history –c Lock the history.
$history –r Unlock history.
$rm.bash_history Removes the history
- Alias is a built-in shell command in Linux/Unix operating systems.
- It can save you a lot of typing by assigning a name to long commands.
- The alias command can be useful if you want to create a ‘shortcut’ to a command.
Syn: Alias name=’command’
$alias U= user add
$alias C= Clear
$alias Display alias list
$unalias U Disable alias
$Vim. bashrc Permanent alias names
For an in-depth understanding of Linux click on