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I would like to run a few commands and give an explicit Ctrl+D, just like, say:

ls;pwd;^D

Unfortunately, the above doesn't work. I've also tried \04 and 0x4 in place of ^D above as mentioned here. These too don't work. How can I achieve this? Also, how is this different from:

ls;pwd;exit
skrowten_hermit
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  • Note that if you type ls;pwd; followed by Ctrl-D (instead of Enter), nothing special happens. Do you want to exit the shell after running those commands? – Kusalananda Dec 11 '19 at 12:03

1 Answers1

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It's partially explained Stéphane Chazelas's answer, so I'll try to quote the relevant parts:

Now, if the current line was empty, and provided the application will have fully read the previously entered lines, the read will return 0 character.

That signifies end of file to the application (when you read from a file, you read until there's nothing more to be read). That's why it's called the eof character, because sending it causes the application to see that no more input is available.

Now, modern shells, at their prompt do not set the terminal in icanon mode because they implement their own line editor which is much more advanced than the terminal driver built-in one. However, in their own line editor, to avoid confusing the users, they give the ^D character (or whatever the terminal's eof setting is with some) the same meaning (to signify eof).

That last line can use a bit more clarification. From the documentation of Bash's line editor, readline:

end-of-file (usually C-d)
The character indicating end-of-file as set, for example, by stty. If this character is read when there are no characters on the line, and point is at the beginning of the line, Readline interprets it as the end of input and returns EOF.

Hence, for readline (and also for most other shells), Ctrl-D is only EOF at the start of a line. So, even if you did manage to add Ctrl-D at the end of that line, it won't be treated as EOF.

And whether EOF will make your interactive shell exit is also a different problem. For bash, this is governed by the IGNOREEOF variable and the set -o ignoreeof option. The variable's documentation says:

Controls the action of the shell on receipt of an EOF character as the sole input. If set, the value denotes the number of consecutive EOF characters that can be read as the first character on an input line before the shell will exit. If the variable exists but does not have a numeric value, or has no value, then the default is 10. If the variable does not exist, then EOF signifies the end of input to the shell. This is only in effect for interactive shells.

Example:

bash-5.0$ IGNOREEOF=
bash-5.0$ <Ctrl-D> Use "exit" to leave the shell.
bash-5.0$ <Ctrl-D> Use "exit" to leave the shell.
bash-5.0$ <Ctrl-D> Use "exit" to leave the shell.
bash-5.0$

Do it 7 more times and it will finally exit.

I don't really see any use for this. If you want to exit the shell at the end of these commands, just use exit.

muru
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