Shell Programming and Scripting

I am getting error in a shell script having a simple date command.
Error is " write to 1 failed [No space left on device] ".
We saw that /tmp folder was 100% full. When we cleared some space in /tmp folder then script worked fine. Why does date command(or any other command) require space in /tmp folder? Which settings define this? Any information on this is appreciated.

Code:

> cat test.ksh
DATE_TMSTP=`date +%Y%m%d_%H%M%S`
> ksh test.ksh
test.ksh: line 1: write to 1 failed [No space left on device]

what is your OS?

OS version is "Red Hat Enterprise Linux Server release 5.10" . Thank you

Is descriptor 1 (stdout) of your current shell redirected to something in /tmp?

Code:

test -t 1 && echo "ok: is terminal"

Do you have an ENV environment variable (where ksh sources its value at startup)?

Code:

echo $ENV

If yes, bypass it with

Code:

ksh -p test.ksh

Is ksh /bin/ksh?

Code:

type ksh

Please find the details you have asked for:

1)

Code:

> test -t 1 && echo "ok: is terminal"
ok: is terminal

2) Nothing defined on $ENV

4)

Code:

> type ksh
ksh is hashed (/bin/ksh)

I am running out of ideas...
One more:

Code:

type date

thanks for your help anyway

Code:

$ type date
date is /bin/date