Tell users exactly what went wrong. Be specific—vague error messages frustrate users.
Not recommended
Bad directory.
Recommended
The specified directory exists but is not writable. To add files to this directory, the directory must be writable. [Explanation of how to make this directory writable.]
Not recommended
Invalid field ‘picture’.
Recommended
The ‘picture’ field can only appear once on the command line; this command line contains the ‘picture’ field
times.
Note: Prior to version 2.1, you could specify the ‘picture’ field more than once, but more recent versions no longer support this.