A bash shell is considered as an interactive shell when it reads and writes data from a user’s terminal. Most startup scripts examine the shell variable called PS1. Usually, PS1 is set in interactive shells, and it is unset in non-interactive shells.
Find out if this shell interactive using PS1
The syntax is as follows:
// Is this Shell Interactive?
[ -z "$PS1" ] && echo "Noop" || echo "Yes"
OR
[ -z "$PS1" ] && echo "This shell is not interactive" || echo "This shell is interactive"
OR
[ -z "$PS1" ] && die "This script is not designed to run from $SHELL" 1 || do_interacive_shell_stuff
You can use bash shell if..else..fi syntax as follows:
if [ -z "$PS1" ]; then die "This script is not designed to run from $SHELL" 1 else //call our function do_interacive_shell_stuff fi |
From the bash reference manual
To determine within a startup script whether or not Bash is running interactively, test the value of the ‘-‘ special parameter. It contains i when the shell is interactive. For example:
case "$-" in *i*) echo "This shell is interactive" ;; *) echo "This shell is not interactive" ;; esac |
tty command
You can also use tty command as follows:
tty -s && echo "This shell is interactive" || echo "This shell is not interactive" ;; |
OR
ssh user@server1.cyberciti.biz tty -s && echo "This shell is interactive" || echo "This shell is not interactive" ;; |
6 comment
Whatever happened to the standard method of checking the fd ‘0’ ???
if [ -t 0 ]; then
# do stuff
fi
Don’t you think that’s a better check that some env variable?
that will miss the action on a fresh login.
Hi,
Very useful article
Thanks a lot..
Full of holes and not reliable at all. PS1 can be defined by someone in their own .bashrc file for instance.
You’d have to stat what /dev/fd/0 points to, and sift out the text that is different.
@ Mike – what other solution do you propose, if -t 0 isn’t enought, nor is [ -z “$PS1” ]
Hi,
How can I create a user with non-interactive shell?
Is it just a matter of:
useradd -s /sbin/nologin lisa
Thanks