Wrapper to allocate a pty (opposite to nohup)

Question

I have a command foo that (for reasons we need not go into) needs to have a pty allocated, i.e. foo succeeds but nohup foo fails.

What is the easiest way to allocate a pty when there is not one? screen -D -m foo seems like overkill, an does not return an exit code (which I need). Save for the exit code, it works.

score 2 · Answer 1 · answered Sep 22 '15 at 14:48

2

Use expect, e.g.

#!/usr/bin/env expect -f

spawn -noecho ssh localhost "sleep 3; false"
catch wait status
exit [lindex $status 3]

answered Sep 22 '15 at 14:48

thrig

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This gives me `/usr/bin/env: ‘expect -f’: No such file or directory`. – CMCDragonkai Jan 23 '19 at 02:59
@CMCDragonkai some unix have broken `env` commands so you'll need to on those systems either change to something without a broken `env` or use the fully qualified path to wherever your vendor puts the `expect` command. – thrig Jan 23 '19 at 14:56

score 2 · Accepted Answer · answered Sep 23 '15 at 06:03

While @thrig's answer would probably work with expect (and I upvoted it), I made a tiny modification to pty.c from Stevens' Advanced Programming in the UNIX® Environment to return the exit code if -r is specified. The result is here. This seems to do the trick with minimal fuss.

score 1 · Answer 3 · answered Aug 26 '21 at 12:48

1

script /dev/null

is the easiest, most portable solution (though still not available by default on android or busybox).

It works fine even when its stdin and stdout are not ttys.

answered Aug 26 '21 at 12:48

`script /dev/null foo` would work on BSD (including macOS). On Linux the syntax is `script -qc foo /dev/null`, as suggested in https://unix.stackexchange.com/a/249726 – Tanz87 Mar 13 '22 at 23:02

Wrapper to allocate a pty (opposite to nohup)

3 Answers3