"nohup" command

[Brad Woolard]

Is the nohup command supposed to stay active after a user logs out? If I type the following command it doesn't stick when the user logs out.

(nohup stty 19200 opost onlcr parenb parodd cs8 ixon -istrip clocal tab3; sleep 200000000)
If anyone has ideas on keeping serial ports open by a different means than the command I issued earlier, I would be glad to give it a try. We have to print checks directly to a device, in case anyone's wondering why I'm bypassing the the print spooler.

Thanks,

Brad Woolard

[Jean-Luc Oudart]

We have a similar script for same reason.
It works fine.
What is the pb ?

nohup(1) nohup(1)

NAME
nohup - run a command immune to hangups

SYNOPSIS
nohup command [arguments]

DESCRIPTION
nohup executes command with hangups and quits ignored. If output is
not redirected by the user, both standard output and standard error
are sent to nohup.out. If nohup.out is not writable in the current
directory, output is redirected to $HOME/nohup.out; otherwise, nohup
fails. If a file is created, the file's permission bits will be set to
S_IRUSR | S_IWUSR.

If output from nohup is redirected to a terminal, or is not redirected
at all, the output is sent to nohup.out.



Jean-Luc

[Brad Woolard]

The problem is it hangs up when the user logs out.

I have to kill the shell process for the user's nohup command to stay intact. If I logout the user that issued the command the printer goes haywire again and prints gibberish.

-Brad

[Jean-Luc Oudart]

I think you nohup the stty but *NOT* the sleep command...
review your command
Jean-Luc

[Sajid_1]

Yes, nohup will keep the programs running even if you logout the session. Do you just want to print to a serial printer?

[Brad Woolard]

Yes, I owuld like to print to the serial printer directly, b/c of the program that utilizes the printer dictactes direct device communication.

-Brad

[A. Clay Stephenson · Accepted solution]

Here's one way to solve it using a small bit of C that I have used for over 20 years to hold a serial port open. I spent about 2 minutes modifying it so that it will compile with the bundled (K & R) C compiler (in case you don't have anything better).

I would add this to /sbin/init.d/Sxxx. You can follow this up will a stty command (preferably in background in the same /sbin/init.d script)to set any other attributes you like.

Compile it like this:

cc holdport.c -o holdport

That will produce a 'holdport' executable.

Invoke it as simply 'holdport' for full usage but typically it would be:

holdport -t /dev/c2a2_lp -s 19200

[Sajid_1]

hi again,

This document has better options with nohup:
http://support1.itrc.hp.com/service/cki/docDisplay.do?docLocale=en_US&docId=200000047674073

Doc ID - S3100002427

[Sajid_1]

hello,

Another document that will do the same function:
http://support1.itrc.hp.com/service/cki/docDisplay.do?docLocale=en_US&docId=200000047992625

Doc ID - KBRC00000859

[Jeff Schussele]

Hi Brad,

Is there a reason why this can't be setup in /etc/inittab - specifically to use the respawn feature?

Could look something like:

cklp:23:respawn:/usr/bin/stty 19200 opost onlcr parenb parodd cs8 ixon -istrip clocal tab3 < /dev/c2a2_lp

I've never set something up like this, but in theory I think it should work.

See man inittab for further details.

HTH,
Jeff

[Brad Woolard]

Awesome responses! I will have to try all of these when I get time to do the testing. We're starting a check run now, but I'm sure when I do try the hold port executable, I will be in business.

Thanks again to all,

Brad Woolard

[Todd Larchuk]

It's been many years since I abandoned the "nohup" command. I NEVER got it to work
correctly under ANY circumstances. Instead I now use "at", which ALWAYS has work great for me and is totally immune to hang-ups.