About

A terminal is an environment for text input/output. Inside the terminal, one runs command-line and text mode programs (including shells).

This tag is about terminals in general; for the Mac OS X Terminal application, use .

Don't confuse the terminal, which is the environment for text mode programs, with the , which executes commands. See also if your problem is accomplishing a task on the command line.

Background

In a unix context, a terminal is an environment for text input and output. Historically, a terminal was a physical device, but these days most terminals are provided by terminal emulators.

If your display is in text mode, this is usually known as a “text console”, or sometimes (somewhat confusingly) as a “virtual terminal”.

A “terminal” can be graphical, but in a unix context there will normally be a qualifier, e.g. “X terminal”.

Most interactive programs run inside terminals are of one of two kinds:

  • read-eval-print loops are programs that read a line, then execute it. Unix shells are examples of this.
  • full-screen text mode programs, such as emacs -nw, lynx, nethack, vi, …

Escape sequences

A terminal and the program inside it communicate by exchanging text with embedded escape sequences. When you type a character in a terminal, the program receives that character; if you type a function key, the terminal usually converts it to an escape sequence. In the other direction, if the program outputs a printable character, the terminal displays it; if the program outputs a control character, it performs a function such as moving the cursor, changing the color, etc. Most terminals are compatible with Xterm control sequences.

Further reading

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