[cups] cupsdStartProcess question

[Michael Sweet]

Dmitry,

> On May 9, 2016, at 1:16 AM, Dmitry Voronin <carriingfate92 at yandex.ru> wrote:
> 
> Hello,
> 
> For my reasons in CUPS I need execute external program and save output into file.
> 
> I determine, that function cupsdStartProcess is more suitable, that system or exec* function.

cupsdStartProcess isn't intended as a general API for user programs, it is an internal function used by the scheduler (cupsd).

posix_spawn is a better alternative (and a portable API) that can handle redirecting stdout to a file.

> 
> So, I have following code:
> 
> outfd = open('/tmp/exec", O_WRONLY);
> 
> status = cupsdStartProcess(command, argv, envp,
>                                         -1 /* intfd */,
>                                          outfd /* opened early */,
>                                          -1 /* errfd */,
>                                          -1 /* backfd */,
>                                          -1 /* sidefd */,
>                                          1 /* execute as root */,
>                                          NULL /* profile */,
>                                          NULL /*job */,
>                                          &pid /* running pid */);
> 
> if (!status)
>  close(outfd);
> else
> {
>  close(outfd);
>  unlink("/tmp/exec");
> }
> 
> When those code is executed, I expect, that in file with fd outfd it was written output of my command. But those file is empty. In /var/spool/cups/tmp/ (I use Debian)
> CUPS create a random file with neede for me output.
> 
> What am I doing wrong?
> 
> Thank you.
> -- 
> Best regards, Dmitry Voronin
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_________________________________________________________
Michael Sweet, Senior Printing System Engineer