Patchwork [manual] Job control is no longer optional.

login
register
mail settings
Submitter Zack Weinberg
Date May 30, 2018, 1:15 a.m.
Message ID <20180530011501.21432-1-zackw@panix.com>
Download mbox | patch
Permalink /patch/27548/
State Committed
Headers show

Comments

Zack Weinberg - May 30, 2018, 1:15 a.m.
The manual contains an entire @node devoted to warning people that job
control is an optional POSIX feature and might not be implemented in
the kernel.  Job control was made mandatory in POSIX.1-2001: compare
<http://pubs.opengroup.org/onlinepubs/7990989775/xsh/unistd.h.html>
with <http://pubs.opengroup.org/onlinepubs/009695399/basedefs/unistd.h.html>.
Seventeen years later, it seems to me we do not need a warning this
loud anymore.

Instead there is a short note in the top-level "Job Control" node
telling people that "old" systems might not support job control and
there's the _POSIX_JOB_CONTROL macro if you really need it.

OK?

        * manual/job.texi (Job Control is Optional): Remove node, as
        job control has not been optional in quite some time.
        (Job Control): Mention briefly that systems older than
        POSIX.1-2001 might not support job control.
        (setpgid): Remove cross-reference to deleted node.
	* manual/conf.texi (_POSIX_JOB_CONTROL): Will always be
        defined on systems conforming to POSIX.1-2001.
---
 manual/conf.texi |  2 ++
 manual/job.texi  | 38 +++++++++-----------------------------
 2 files changed, 11 insertions(+), 29 deletions(-)
Zack Weinberg - Oct. 17, 2018, 5:41 p.m.
Ping?
On Tue, May 29, 2018 at 9:15 PM Zack Weinberg <zackw@panix.com> wrote:
>
> The manual contains an entire @node devoted to warning people that job
> control is an optional POSIX feature and might not be implemented in
> the kernel.  Job control was made mandatory in POSIX.1-2001: compare
> <http://pubs.opengroup.org/onlinepubs/7990989775/xsh/unistd.h.html>
> with <http://pubs.opengroup.org/onlinepubs/009695399/basedefs/unistd.h.html>.
> Seventeen years later, it seems to me we do not need a warning this
> loud anymore.
>
> Instead there is a short note in the top-level "Job Control" node
> telling people that "old" systems might not support job control and
> there's the _POSIX_JOB_CONTROL macro if you really need it.
>
> OK?
>
>         * manual/job.texi (Job Control is Optional): Remove node, as
>         job control has not been optional in quite some time.
>         (Job Control): Mention briefly that systems older than
>         POSIX.1-2001 might not support job control.
>         (setpgid): Remove cross-reference to deleted node.
>         * manual/conf.texi (_POSIX_JOB_CONTROL): Will always be
>         defined on systems conforming to POSIX.1-2001.
> ---
>  manual/conf.texi |  2 ++
>  manual/job.texi  | 38 +++++++++-----------------------------
>  2 files changed, 11 insertions(+), 29 deletions(-)
>
> diff --git a/manual/conf.texi b/manual/conf.texi
> index f1dce4aa44..51fb2f5aa1 100644
> --- a/manual/conf.texi
> +++ b/manual/conf.texi
> @@ -156,6 +156,8 @@ supported; use @code{sysconf} to find out.  @xref{Sysconf}.
>  If this symbol is defined, it indicates that the system supports job
>  control.  Otherwise, the implementation behaves as if all processes
>  within a session belong to a single process group.  @xref{Job Control}.
> +Systems conforming to the 2001 revision of POSIX, or newer, will
> +always define this symbol.
>  @end deftypevr
>
>  @deftypevr Macro int _POSIX_SAVED_IDS
> diff --git a/manual/job.texi b/manual/job.texi
> index 944967a73d..e304313ca7 100644
> --- a/manual/job.texi
> +++ b/manual/job.texi
> @@ -19,9 +19,15 @@ You need to be familiar with concepts relating to process creation
>  Handling}) in order to understand this material presented in this
>  chapter.
>
> +@vindex _POSIX_JOB_CONTROL
> +Some old systems do not support job control, but @gnusystems{} always
> +have, and it is a required feature in the 2001 revision of POSIX.1
> +(@pxref{POSIX}).  If you need to be portable to old systems, you can
> +use the @code{_POSIX_JOB_CONTROL} macro to test at compile-time
> +whether the system supports job control.  @xref{System Options}.
> +
>  @menu
>  * Concepts of Job Control::     Jobs can be controlled by a shell.
> -* Job Control is Optional::     Not all POSIX systems support job control.
>  * Controlling Terminal::        How a process gets its controlling terminal.
>  * Access to the Terminal::      How processes share the controlling terminal.
>  * Orphaned Process Groups::     Jobs left after the user logs out.
> @@ -29,7 +35,7 @@ chapter.
>  * Functions for Job Control::   Functions to control process groups.
>  @end menu
>
> -@node Concepts of Job Control, Job Control is Optional,  , Job Control
> +@node Concepts of Job Control
>  @section Concepts of Job Control
>
>  @cindex shell
> @@ -102,30 +108,7 @@ jobs between foreground and background.
>  @xref{Access to the Terminal}, for more information about I/O to the
>  controlling terminal.
>
> -@node Job Control is Optional, Controlling Terminal, Concepts of Job Control , Job Control
> -@section Job Control is Optional
> -@cindex job control is optional
> -
> -Not all operating systems support job control.  @gnusystems{} do
> -support job control, but if you are using @theglibc{} on some other
> -system, that system may not support job control itself.
> -
> -You can use the @code{_POSIX_JOB_CONTROL} macro to test at compile-time
> -whether the system supports job control.  @xref{System Options}.
> -
> -If job control is not supported, then there can be only one process
> -group per session, which behaves as if it were always in the foreground.
> -The functions for creating additional process groups simply fail with
> -the error code @code{ENOSYS}.
> -
> -The macros naming the various job control signals (@pxref{Job Control
> -Signals}) are defined even if job control is not supported.  However,
> -the system never generates these signals, and attempts to send a job
> -control signal or examine or specify their actions report errors or do
> -nothing.
> -
> -
> -@node Controlling Terminal, Access to the Terminal, Job Control is Optional, Job Control
> +@node Controlling Terminal
>  @section Controlling Terminal of a Process
>
>  One of the attributes of a process is its controlling terminal.  Child
> @@ -1166,9 +1149,6 @@ The @code{setpgid} function puts the process @var{pid} into the process
>  group @var{pgid}.  As a special case, either @var{pid} or @var{pgid} can
>  be zero to indicate the process ID of the calling process.
>
> -This function fails on a system that does not support job control.
> -@xref{Job Control is Optional}, for more information.
> -
>  If the operation is successful, @code{setpgid} returns zero.  Otherwise
>  it returns @code{-1}.  The following @code{errno} error conditions are
>  defined for this function:
> --
> 2.17.0
>
Paul Eggert - Oct. 17, 2018, 5:55 p.m.
Thanks, this patch looks good to me.
Zack Weinberg - Oct. 17, 2018, 6:13 p.m.
On Wed, Oct 17, 2018 at 1:55 PM Paul Eggert <eggert@cs.ucla.edu> wrote:
>
> Thanks, this patch looks good to me.

Thanks for looking at it.  Committed.

zw

Patch

diff --git a/manual/conf.texi b/manual/conf.texi
index f1dce4aa44..51fb2f5aa1 100644
--- a/manual/conf.texi
+++ b/manual/conf.texi
@@ -156,6 +156,8 @@  supported; use @code{sysconf} to find out.  @xref{Sysconf}.
 If this symbol is defined, it indicates that the system supports job
 control.  Otherwise, the implementation behaves as if all processes
 within a session belong to a single process group.  @xref{Job Control}.
+Systems conforming to the 2001 revision of POSIX, or newer, will
+always define this symbol.
 @end deftypevr
 
 @deftypevr Macro int _POSIX_SAVED_IDS
diff --git a/manual/job.texi b/manual/job.texi
index 944967a73d..e304313ca7 100644
--- a/manual/job.texi
+++ b/manual/job.texi
@@ -19,9 +19,15 @@  You need to be familiar with concepts relating to process creation
 Handling}) in order to understand this material presented in this
 chapter.
 
+@vindex _POSIX_JOB_CONTROL
+Some old systems do not support job control, but @gnusystems{} always
+have, and it is a required feature in the 2001 revision of POSIX.1
+(@pxref{POSIX}).  If you need to be portable to old systems, you can
+use the @code{_POSIX_JOB_CONTROL} macro to test at compile-time
+whether the system supports job control.  @xref{System Options}.
+
 @menu
 * Concepts of Job Control::     Jobs can be controlled by a shell.
-* Job Control is Optional::     Not all POSIX systems support job control.
 * Controlling Terminal::        How a process gets its controlling terminal.
 * Access to the Terminal::      How processes share the controlling terminal.
 * Orphaned Process Groups::     Jobs left after the user logs out.
@@ -29,7 +35,7 @@  chapter.
 * Functions for Job Control::   Functions to control process groups.
 @end menu
 
-@node Concepts of Job Control, Job Control is Optional,  , Job Control
+@node Concepts of Job Control
 @section Concepts of Job Control
 
 @cindex shell
@@ -102,30 +108,7 @@  jobs between foreground and background.
 @xref{Access to the Terminal}, for more information about I/O to the
 controlling terminal.
 
-@node Job Control is Optional, Controlling Terminal, Concepts of Job Control , Job Control
-@section Job Control is Optional
-@cindex job control is optional
-
-Not all operating systems support job control.  @gnusystems{} do
-support job control, but if you are using @theglibc{} on some other
-system, that system may not support job control itself.
-
-You can use the @code{_POSIX_JOB_CONTROL} macro to test at compile-time
-whether the system supports job control.  @xref{System Options}.
-
-If job control is not supported, then there can be only one process
-group per session, which behaves as if it were always in the foreground.
-The functions for creating additional process groups simply fail with
-the error code @code{ENOSYS}.
-
-The macros naming the various job control signals (@pxref{Job Control
-Signals}) are defined even if job control is not supported.  However,
-the system never generates these signals, and attempts to send a job
-control signal or examine or specify their actions report errors or do
-nothing.
-
-
-@node Controlling Terminal, Access to the Terminal, Job Control is Optional, Job Control
+@node Controlling Terminal
 @section Controlling Terminal of a Process
 
 One of the attributes of a process is its controlling terminal.  Child
@@ -1166,9 +1149,6 @@  The @code{setpgid} function puts the process @var{pid} into the process
 group @var{pgid}.  As a special case, either @var{pid} or @var{pgid} can
 be zero to indicate the process ID of the calling process.
 
-This function fails on a system that does not support job control.
-@xref{Job Control is Optional}, for more information.
-
 If the operation is successful, @code{setpgid} returns zero.  Otherwise
 it returns @code{-1}.  The following @code{errno} error conditions are
 defined for this function: