Script/cron error

Bab00shka · #1 (**permalink**) 06-12-2002

I am running a script through cron but keep getting this message in unix mail:

Subject: cron

Not a terminal
stty: : Not a typewriter
stty: : Not a typewriter
logout

The script appears to run successfully. Any ideas what this message is and how I can stop it?

killerserv · #2 (**permalink**) 06-12-2002

The not-a-typewriter error is caused by running commands where there is no controlling tty device; that is, no interactive terminal is present. This would be true for a script that runs in cron or has su - to run a batch job.

To prevent this, you need to start with /etc/profile and test for an interactive tty device as in:

Code:

case $- in

            *i* ) export INTERACTIVE=/sbin/true

                              ;;

                        * ) export INTERACTIVE=/sbin/false

                              ;;

esac

While this may seem cryptic, the shell understands whether it is interactive or not and sets a flag (the i flag). The construct $- returns all the current flags that are set as a string and if the letter i appears in the string, the shell is interactive. Another way is to test the terminal device with the tty(1) command as in:

Code:

if tty -s

then

         export TTY=/sbin/true

else

         export TTY=/sbin/false

fi

The choice of $TTY or $INTERACTIVE is arbitrary as far as names. In your /etc/profile (and .profile, etc.), you can then test for interactive terminal prior to any settings that affect the terminal. A few of the common commands are: stty, tput, and tabs. Here is an example:

Code:

if [ $TTY ]

then

     /sbin/stty erase "^H" kill "^U"

     /sbin/stty intr "^C" eof "^D"

     /sbin/stty -parity ixoff

     /sbin/stty susp \^Z dsusp \^Y

if [ -x /usr/bin/tabs ]

then

     /usr/bin/tabs

else

     echo "$0: The command \"/usr/bin/

               tabs\" was not found."

 fi

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