# Identify the error's cause

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Tell users exactly what went wrong. Be specific---vague error messages
frustrate users.

Not recommended
> Bad directory.

Recommended
> The *\[Name of directory\]* 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 *\<N\>* times.  
> Note: Prior to version 2.1, you could specify the 'picture' field more than once, but more recent versions no longer support this.

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**Next unit:** [Identify the user's invalid inputs](https://developers.google.com/tech-writing/error-messages/invalid-inputs)