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Re: (ITS#6038) Write slapadd progress meter to stdout

Rein Tollevik wrote:
> hyc@symas.com wrote:
>> Hallvard B Furuseth wrote:
>>> hyc@symas.com writes:
>>>> Just redirect stdin, and the meter will automatically turn itself off.
>>> It was stderr, not stdin - which after all can be the ldif.
>>> Stdout is better.
>> No, you misunderstand.
>> Redirecting stderr (or stdout) merely sends the progress info to that
>> destination. Piping input on stdin will turn it off, so there's no progress
>> info to redirect.
> No, the code only enables the meter if stdout (was: stderr) is a tty, so
> redirecting it anywhere disables it.  The meter was enabled both by
> "slapadd -l file" and "slapadd<  file", but "cat file | slapadd" did
> disable it.  IMHO not exactly an obvious way..
> An option sounds more and more like the solution, what about "-m" for
> meter?  Though I'm not sure whether I prefer that it should be enabled
> by default and the option disable it, or the other way around..

We already decided it should be enabled by default. Setting any explicit debug 
flag already disables it.

>> Writing progress to stderr is the correct thing to do, because it's transient
>> info that isn't meant to be saved. Checking whether stdout is redirected or
>> not is fine, but writing progress info to stdout is not.
> For programs that produce real output (slapcat, ldapsearch) this might
> be true, but for those that don't (slapadd, slapd) I totally disagree.
> Stderr is for errors, not chatty progress or debug messages. I always
> hate it when the error messages gets burried in lots of noice.

Stderr is for any diagnostic info. Progress reports are diagnostic, they are 
certainly not the main purpose of any of these programs. Stdout is for 
anything related to the primary purpose of these programs. For slapcat, that's 
obvious. For slapadd/slapindex, these programs' purpose is not to produce any 
textual output at all; stdout is unused. That doesn't mean it's correct to 
ignore these long-standard Unix I/O usage conventions and suddenly switch 
stderr output to stdout.

And as already noted, if you're looking for debug messages, then the meter 
will be disabled.

> My preference is to have progress and debug messages on stdout, enabled
> by options or at least possible to disable by options.

Quite simply, this is completely wrong. It also introduces an unnecessary 
inconsistency between slapcat and slapadd behavior. Progress belongs on 
stderr, period.

   -- Howard Chu
   CTO, Symas Corp.           http://www.symas.com
   Director, Highland Sun     http://highlandsun.com/hyc/
   Chief Architect, OpenLDAP  http://www.openldap.org/project/