Data Validation

Required Field

Reject Empty Text

A required field should be checked before the script builds commands or summaries from it.

Program

Play the script to choose a field value and see the validation message.

required_field.sh 
#!/usr/bin/env bash

owner=
if [ -n "$owner" ]; then
    message="owner=$owner"
else
    message="missing-owner"
fi
echo "$message"

#!/usr/bin/env bash

owner=
if [ -n "$owner" ]; then
    message="owner=$owner"
else
    message="missing-owner"
fi
echo "$message"
required field A required value must be present before the script continues.
non-empty test `[ -n "$owner" ]` checks that the string has length.
error message A named failure message gives callers a clear correction.