SAP Note 17256 - Job log message "Exec format error"

Symptom:

When you execute an external program within a job, the job terminates. The job log contains the message:
'Ext. Prog.: Exec format error'

Cause and prerequisites

The program for execution is an interpreter file (e.g. a shell script) which does not have an interpreter ID.

Solution
Correct the interpreter file.
According to man-page of the exec() command, an interpreter file must be defined as follows:
An interpreter file is a text file that begins with the line
#! pathname [arg]
Typical example: #! /bin/sh
This line must(!) be contained at the very start of the interpreter file, otherwise the operating system cannot tell how to interpret the file.
Other examples:
#! /bin/csh
#! /bin/awk -f