Error message output

[Manish Jain]

On 2020-09-20 22:41, Polytropon wrote:
> I have a general question. Is it still considered useful to
> output error messages of a script to standard error?
> 
> Example:
> 
> 	if [ something not okay ]; then
> 		echo "the error message" > /dev/stderr
> 		exit 1
> 	fi
> 
> While progress messages will per default go to standard output,
> error messages should be printed to standard error. The reason:
> If a program is silenced to > /dev/null, error messages will
> still be visible (no "silent failing"); if a user wants to
> explicitely mute all messages, > /dev/null 2>&1 has to be
> specified for the redirection. The judgement if a message is
> a regular progress message, an information about some slightly
> problematic case, or a real fatal error depends on the programmer.
> For example:
> 
> 	echo "${FILE] processed, ${RECS} records counted."
> 	 -> standard output
> 
> 	echo "${DIR} already checked, skipping."
> 	 -> standard output (non-fatal error"
> 
> 	echo "${DEV} is read only, aborting."
> 	exit 1
> 	 -> standard error (fatal error)
> 
> 	echo "Cannot start: Input filename missing."
> 	usage()
> 	exit 1
> 	 -> standard error (fatal error)
> 
> At least that's what I've learned centuries ago.
> 
> Is that still valid?
> 
> 

Fully valid. Whenever I write any C code, those are the guidelines I 
adhere to myself.

Regards,
Manish Jain