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

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What is the exact difference between a 'terminal', a 'shell', a 'tty' and a 'console'?

I think these terms almost refer to the same thing, when used loosely: terminal shell tty console What exactly does each of these terms refer to?
171
votes
3answers
90k views

How to unfreeze after accidentally pressing Ctrl-S in a terminal?

It's a situation that has happened quite often to me: after I press (with a different intention) Ctrl-S in a terminal, the interaction (input or output) with it is frozen. It's probably a kind of ...
111
votes
7answers
80k views

How can I close a terminal without killing the command running in it?

Sometimes I want to start a process and forget about it. If I start it from the command line, like this: redshift I can't close the terminal, or it will kill the process. Can I run a command in ...
102
votes
6answers
121k views

How to split the terminal into more than one “view”?

From vi, if you issue the command :sp, the screen splits into two "views", allowing you to edit more than one file from the same terminal. Along those same lines, is there a way to have multiple ...
101
votes
7answers
12k views

How to kill a runaway cat?

Many times I accidentally run the cat command on files that have contents up to few thousand lines. I try to kill the cat command with Ctrl+ C or Ctrl+Z, but both only take effect after the total ...
91
votes
8answers
44k views

How can I disown a running process and associate it to a new screen shell?

I have a running program on a SSH shell. I want to pause it and be able to unpause its execution when I come back. One way I thought of doing that was to transfer its ownership to a screen shell, ...
77
votes
3answers
10k views

Watch YouTube videos in terminal

Like the title says it, I'm looking for a way to watch YouTube videos in terminal (not in a browser or another window, but right there, in any bash session). Is there a simple way to do this? I ...
69
votes
4answers
10k views

What is the point of CTRL-s?

CTRL+s stops all output to the terminal which can be restarted with CTRL+q. But, why does CTRL+s exist in the first place? What problem was trying to be solved by putting that control sequence in ...
57
votes
7answers
3k views

How safe is it to cat an arbitrary file?

Sometimes when I cat a binary file by mistake, my terminal gets garbled up. Nothing a quick reset can't fix, but couldn't an attacker theoretically create a file that, when displayed on a terminal, ...
56
votes
2answers
3k views

Clear / erase a mistyped invisible password on a shell / terminal in Linux

One thing that annoys me using Linux's terminal is when I have to type a invisble password, like when you run ssh. Sometimes I mistype one or more letters and then I have to press backspace key a few ...
55
votes
4answers
62k views

How to display `top` results sorted by memory usage in real time?

How can I display the top results in my terminal in real time so that the list is sorted by memory usage?
47
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2answers
22k views

Ctrl-s hang terminal emulator?

I came across a sentence in vimdoc: Note: CTRL-S does not work on all terminals and might block further input, use CTRL-Q to get going again. and this key indeed hangs my vim. I was ...
45
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6answers
5k views

Can I configure my shell to print STDERR and STDOUT in different colors?

I want to set my terminal up so stderr is printed in a different color than stdout; maybe red. This would make it easier to tell the two apart. Is there a way to configure this in .bashrc? If not, is ...
44
votes
1answer
8k views

Kill an unresponsive ssh session without closing the terminal

Is there a way to disconnect from an SSH session that has become unresponsive without killing the whole terminal? Specifically I'm using konsole, and the machine I'm working with sometimes hangs, but ...
42
votes
3answers
50k views

How to recover a 'lost' screen session?

Somehow I managed to close a screen window without screen 'noticing' it, so the session is still flagged as attached. This prevents me from re-attaching to this session. What can I do? ...
40
votes
3answers
18k views

How can I break away from an SSH session that has crashed?

Many times I have an SSH session that doesn't respond anymore (for example, when I lose internet connection and then reconnect). Ctrl+C, Ctrl+D, Ctrl+Z and a zillion of key presses don't have any ...
37
votes
2answers
4k views

Can a terminal emulator be as fast as TTY 1-6?

I've been trying various terminal emulators lately, from the built-in gnome-terminal, aterm, xterm, wterm, to rxvt. The test I've been doing is in this order: Open up a tmux window with 2 panes The ...
34
votes
2answers
74k views

List all connected SSH sessions?

I just SSH'd into root, and then SSH'd again into root on the same machine. So I have two windows open both SSH'd into root on my remote machine. From the shell, how can I see a list of these two ...
32
votes
1answer
1k views

What happens when Ctrl + Alt + F<Num> is pressed?

I am looking for an explanation of what happens in Linux when this key combination is pressed to change the current terminal. In particular, what software component intercepts this key combination and ...
29
votes
3answers
97k views

How to append multiple lines to a file with bash

I am writing a bash script to look for a file if it doesn't exist then create it and append this to it: Host localhost ForwardAgent yes So "line then new line 'tab' then text" I think its a ...
29
votes
4answers
3k views

What are the responsibilities of each Pseudo-Terminal (PTY) component (software, master side, slave side)?

I am trying to figure out how a tty works1 (the work-flow and responsibilities of each elements). I have read several interesting articles about it, but there are still some blurry areas. This is ...
28
votes
5answers
2k views

How does clear command work?

I was recently trying to learn more about how the shell works and was looking at how the clear command works. The executable is located in /usr/bin/clear and it seems to print out a bunch of blank ...
28
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3answers
30k views

SSH inside SSH fails with “stdin: is not a tty”

I'm trying to connect to machine one with ssh and then connect to another machine two with ssh, but I get this error. ssh user@computerone.com 'ssh otheruser@computertwo.com' stdin: is not a tty ...
26
votes
6answers
23k views

How to clear terminal completely?

When we use clear command or Ctrl+L in terminal, it clears terminal but we can still scroll back to view the last used commands. Is there a way to completely clear the terminal?
25
votes
7answers
24k views

Disable screen blanking on text console

I'm running linux clusters, mostly on SLES10. The servers are mostly blades, accessed via remote console. There is a real console in the server room, but switched off. I would like to disable the ...
25
votes
3answers
21k views

Scroll inside Screen, or Pause Output

I use screen for my command-line tasks while managing the servers where I work. I usually run small commands (mostly file-system tasks) but sometimes I run more extensive tasks (like DBA). The output ...
24
votes
5answers
94k views

How to find application's path from command line?

For example, I have git installed on my system. But I don't remember where I installed it, so which command is fit to find this out?
24
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4answers
15k views

How to remove “You have mail” welcome message

When I open up my terminal it says "you have mail", anyone has any idea of why? I am running OS X, but since it too is based on Unix and relies on files such as bashrc, bash_profile etc. I thought ...
23
votes
4answers
20k views

How to scroll in a terminal using keyboard?

How can I scroll in bash using only the keyboard? If it's not possible in bash, are there any other shells that support this?
23
votes
6answers
4k views

Using VI keys to edit shell commands in UNIX

I used to have a co-worker who was really good at UNIX. He showed me how to use Vi key bindings to edit my shell commands. He placed the command in a file that ran every time I logged in. Since ...
23
votes
2answers
11k views

Output from ls has newlines but displays on a single line. Why?

I think I may be overlooking a relatively fundamental point regarding shell. Output from the ls command by default separates output with newlines, but the shell displays the output on a single line. ...
23
votes
3answers
16k views

What are pseudo terminals (pty/tty)?

This might be really basic question but I want to understand it thoroughly. What is a pseudo terminal? (tty/pty) Why do we need them? How they got introduced and what was the need for it? Are they ...
22
votes
8answers
98k views

How to connect to a serial port as simple as using SSH?

Is there a way to connect to a serial terminal just as you would do with SSH? There must be a simpler way than tools such as Minicom, like this $ serial /dev/ttyS0 I know I can cat the output ...
22
votes
4answers
25k views

How to attach terminal to detached process?

I have detached a process from my terminal, like this: $ process & That terminal is now long closed, but process is still running and I want to send some commands to that process's stdin. Is ...
22
votes
2answers
23k views

How to signal the end of stdin input in bash

In Bash, I learned that the ending signal can be changed by here document. But by default how can I signal the end of stdin input? I happened to find that with cat and chardet, their stdin inputs can ...
22
votes
6answers
14k views

Removing control chars (including console codes / colours) from script output

I can use the "script" command to record an interactive session at the command line. However, this includes all control characters and colour codes. I can remove control characters (like backspace) ...
22
votes
4answers
20k views

Dark blue color in vim or ls output in linux

I have a problem with dark-blue color in vim or ls output. Because I'm using black background color, words colored in dark-blue are almost completely invisible. How can I address this problem?
21
votes
6answers
10k views

How to check if bash can print colors

I want to know if there's any way to check if my program can output terminal output using colors or not. Running commands like less and looking at the output from a program that outputs using ...
21
votes
3answers
64k views

What is the best text-mode browser? [closed]

I am looking for one that is updated frequently and has support for many things. Please also state how to install it.
21
votes
3answers
13k views

Which terminal type am I using?

I have tested this with both Ubuntu 12.04 and Debian 7. When I do echo $TERM I get xterm But if I use the dropdown menu "help" > "about" then it says gnome terminal 3.4.1.1. Does this mean I am ...
20
votes
5answers
6k views

How can I create an alias for a git [action] command (which includes spaces)?

Most of my my aliases are of this form: alias p='pwd' I want to alias git commit so that it does git commit -v But trying to create an alias with a space gives an error: $ alias 'git commit'='git ...
20
votes
5answers
957 views

How can I find the common name for a particular glyph?

Sometimes, I'd like to know the name of a glyph. For example, if I see −, I may want to know if it's a hyphen -, an en-dash –, an em-dash —, or a minus symbol −. Is there a way that I can copy-paste ...
19
votes
2answers
1k views

Are the terminal color escape sequences defined anywhere for bash?

I've used every so often colors in Bash scripting (mostly on CentOS), but to make their usage more convinient I end up redefining variables to color values: local GRAY="\[\033[1;30m\]" local ...
19
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3answers
18k views

What is stored in /dev/pts files and can we open them?

According to my knowledge, /dev/pts files are created for ssh or telnet sessions.
19
votes
2answers
3k views

How do I start all shell sessions in a directory other than $HOME?

When I open my non-login shell in Ubuntu, my present working directory is /home/user_name (my $HOME environment variable), but I want to change this such that when I start my terminal I am in some ...
19
votes
4answers
4k views

What happens to the output of a process that has been disowned and lost its terminal?

If I close the virtual terminal, where some process was started, does the output just go straight to /dev/null, or can it pollute memory somehow? Can I anyhow grab the output to continue reading it at ...
18
votes
4answers
2k views

How to know the “level” of shells I am in?

If I open a terminal like xterm I will have a shell. Then if I use ssh or zsh I will have another "level" of shell. Is there a way to know how many times I have to Ctrl+D or type exit to exit all of ...
18
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3answers
14k views

tmux, TERM and 256 colours support

Introduction My question arises from the necessity of understanding why I have now (after multiple trials) Terminal and tmux supporting 256 colours and tput colors telling me there are only 8 of ...
17
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9answers
2k views

How to make sure that a command is not interrupted, even if terminal is closed? [duplicate]

In Linux. Say I want to run a command and it takes too long. I just want to ensure it's done. How?
17
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5answers
10k views

How can I close a terminal without killing its children (without running `screen` first)?

sometimes I run an app in the gnome-terminal, but then I suddenly have to restart gnome or something. I guess the answer to the question is also useful then I want to disconnect from SSH where ...