Checking if 'we' are running in an interactive shell....

[Charles Harris]

Dear all,

Just a quick question, I used to have a script floating about that could determin if a shell was interactive or not (ie run by cron etc). Please would some kind soul remind me how it's done?

All pointers / tips / RTFF etc warmly received as ever!

Cheers,

-=ChaZ=-

[James R. Ferguson · Accepted solution]

Hi Charles:

# [ -t 0 ] && echo "Interactive"

Regards!

...JRF...

[Jonathan Fife]

For ksh I use:

if [[ $- = *i* ]]; then
#interactive shell
else
#non-interactive shell
fi

[spex]

# typeset INTERACTIVE=0 && [ -t 0 ] && INTERACTIVE=1

[A. Clay Stephenson]

The standard test for this is to determine if stdin (file descriptor 0) is associated with a tty (terminal-like) device so:

if [ -t 0 ]
then
echo "We are interactive"
else
echo "We ain't no interactive active session nohow"
fi

or better (because the external test command is replaced with the shell's internal test):

if [[ -t 0 ]]
then
echo "We are interactive"
else
echo "We ain't no interactive active session nohow"
fi
-------------------------------
In any event, testing to see if stdin is a tty device is a standard UNIX idiom.

[Charles Harris]

Thanks guys, I knew I was having a 'moment' it's still Monday here after all!!

Cheers!

-=ChaZ=-

[Bill Hassell]

Actually, I like this:

if tty -s
then
...interactive stuff...
fi

Highly portable among POSIX shells like ksh, HP's sh, bash, etc since an external command is used to determine the interactive status.