Script returned no value problem for external check

[dsh]

Hy,

I have a problem regarding external checks.
I wrote a little shell script the gets the software version number of a device.

#!/bin/sh

#writes the sw version number in the file "sw_version"
./get_webio_sw_version.sh

#print the sw version 
tail sw_version

#delete temp files
rm -f sw_version
rm -f httpresponse

#debug
#echo 2.26

When I execute the script manually it works fine, also with zabbix user.
But when I create an item for this, it became not supported because script returned no value.
If I enable the last line and echo the version number in that way it also works in zabbix.
I also tried once to read the version number in a variable and echo this variable, but was the same problem. Why does it work when I echo a hardcoded value.
Hope anybody can help me.

UPDATE: there must be some problem with reading from files, but no idea why.

br

[dsh]

Mea Culpa

I just forgot to use absolute path for the other files.
Such a newbie failure.