BASH detaching from tty when run in background with '&'

[akaKul]

Hi
I have a bash script that I need to run both interactivly and non-interactivly (ie via crond or using '&').
This script echo's my lovely junk to the terminal if run interactivly, or to a file if run via crond.
I use: (Which works fine!!)
if [ -z $(tty) ]; then
exec > the_file 2>&1
fi

However I need the bash script to also be able to completly detach from the tty/pts session when run in the background ... ie ./script.sh & Which currently it is still aware that it has a terminal attaxched and displays the results to the tty/pts terminal

Any ideas how i can convince the script it is NOT running interactivly when it is run using '&' ?

Many Thanks
Kul

 

[mrregan]

Hi,
How about passing a parameter to the script:
script.sh bg
----------------------------
case "$1"
bg) ..background commands
*) ..anything else - foreground commands
esac

 

[mrn]

nohup script.sh & --
| Mike Nixon
| Unix Admin
|

http://www.instantflashshop.com

----------------------------

 

[akaKul]

Hiyas,

Ok the parameter thing will undoubtly work, but is a little cumbersome and eextreemly likely i will forget to use it

Using 'nohup' doesnt unfortunatly detach the job from the issuing terminal fully, the session is inherrited and means that the 'tty' type woudl aalso be inherrited

So....
After searching for the whole day on the net with every conceivable combination of search patterns, I have concluded there is nothing about this, and bash doesn't have this facility built in

So now my BASH does(will)....
Here is 'a' solution, and VERY workable, providing exactly what I need:

file blah.c
#include <termios.h>
#include <stdlib.h>
int main( void ) {
struct termios term;
tcgetattr(2, &term);
if (!(term.c_lflag & ECHO))
exit(0);
exit(1);
}

gcc blah.c -o blah
chmod 700 blah

in my script....
./blah
if [ $? -eq 0 ]; then
exec > the_file 2>&1
fi

(in addition/combination to the original mail!)


Now we can tell if there is a terminal attached to the job, even when executed using the 'nohup' and/or '&', or even if run from 'at', 'batch' or 'crond'. Regards, Kul

http://camelbackup.com/

Need Very FAST Dial-Up Access:

http://www.cameldial.co.uk/

 

[ProbablyDown]

Hey Kul,

I had a similar issue where my proc would die when I exited. My final solution was to start a second session and kill -9 the first shell. So in steps:

1)nohup script.sh &
2)Start new session
3)ps -u <username> (note the shell start time)
4)kill -9 <pid> (where pid is the first shell poc number)

I know it's messy but it worked for me! ...and oddly enough, I don't always have to do this...

Good luck!
-pd