Os - Shell

This page is about shell in an OS context

A shell is a command line interpreter for OS Command.

In a more detailed way, a shell is:

• an interactive application
• providing a read-eval-print loop environment (REPL)
• for
  • built-in command of the operating system kernel
  • and third party command from executable
• in a terminal

Each time:

• we launch a shell, the operating system creates a new process.
• the shell starts a third party command, the shell creates a new process / thread.

• Windows:
  • Dos (Win32 Shell Scripting) and Utilities
  • PowerShell
• Linux - Shell
  • Bash - Bash cli
• More … Operating_system_shells

You can access shell remotely with the following application protocol

• SSH (secured)
• Telnet (non-secured)

• tab-completion,
• command history

Every extension file has a color. See

dircolors

LS_COLORS='
rs=0:di=01;
34:ln=01;
36:mh=00:pi=40;
33:so=01;
35:do=01;
35:bd=40;
33;
01:cd=40;
33;
01:or=40;
31;
01:su=37;
41:sg=30;
43:ca=30;
41:tw=30;
42:ow=34;
42:st=37;
44:ex=01;
32:*.tar=01;
31:*.tgz=01;
31:*.arc=01;
31:*.arj=01;
31:*.taz=01;
31:*.lha=01;
31:*.lz4=01;
31:*.lzh=01;
...;

export LS_COLORS

• The colors numbers are Terminal Colors number