Category OS

Shells

Shell is a program taking commands from a keyboard and giving them to operating system. Below are three popular shells on Linux. bash Bourne ...

Virtual Consoles

Virtual Consoles enable multi-user logins on a single machine. For example, you can login with your account and also as a root.   By ...

Down Call vs. Up Call

Down Call User code(unprivileged) enters to kernel with trap(interrupt). Up Call Kernel(privileged) enters to user code with IPC(Interprocess ...

Hard Link vs. Soft Link

Hard links are just different names for the same file. One file can have many different names or hard links. Both original file and link file ...

Linux Hierarchy Structure

The Root Directory is the starting point of the file system hierarchy. Everything in the system, including the other directories and files of the ...

Chmod

A chmod is used to change permission of files and directories. form:     chmod  [options]  permissions  filename can be represented in two ways. ...

Alias

An alias is a (usually short) name that the shell translates into another (usually longer) name or command. Aliases allow you to define new ...

tee command

less command on the picture is used to display information to the terminal one page at a time. less is faster than other command because it ...