[Bug 264971] tcsetpgrp(3) manpage should mention the relation with SIGTTOU

From: <bugzilla-noreply_at_freebsd.org>
Date: Fri, 01 Jul 2022 08:37:21 UTC

            Bug ID: 264971
           Summary: tcsetpgrp(3) manpage should mention the relation with
           Product: Documentation
           Version: Latest
          Hardware: Any
                OS: Any
            Status: New
          Severity: Affects Only Me
          Priority: ---
         Component: Manual Pages
          Assignee: bugs@FreeBSD.org
          Reporter: bsdpr@phoe.frmug.org
                CC: doc@FreeBSD.org

I recently had some difficulties when trying to use tcsetpgrp(3) from a process
trying to bring itself as the foreground process group leader of its
controlling terminal. The process got a SIGTTOU sent, that was unexpected as
this signal is not mentioned at all in the tcsetpgrp(3) manpage. I eventually
found an enlightening mention of this signal and how to handle it in an
unanticipated location, the manual of an old release of the SAS/C compiler.

"If tcsetpgrp is called from a background process, the signal SIGTTOU is
generated, unless the signal is ignored or blocked. If the signal is defaulted,
this will cause the calling process to stop. If the signal is handled,
tcsetpgrp will set errno to EINTR and fail. For this reason, you should ignore
or block SIGTTOU if you call tcsetpgrp from a background process."


I think an explanation of the role of SIGTTOU and its usage relative to
tcsetpgrp(3) should be added to the manual page as it plays an important role
in the correct application of this library function.

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