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List:       busybox
Subject:    Re: ash: support "set -m" monitor mode even when not interactive
From:       steffen <steffen () sdaoden ! eu>
Date:       2024-04-08 23:01:07
Message-ID: 20240408230107.DC94612D8D7 () kent ! sdaoden ! eu
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Hello.

There was no answer to

Steffen Nurpmeso wrote in
 <20230117202731.6q006%steffen@sdaoden.eu>:
 |This came up on the dash list, and so i took over Jilles
 |Tjoelker's FreeBSD commit from 2014 to busybox ash.
 |Note i have no idea of what i am doing, but from testing it seems
 |to work; i have simply taken it over, which is a cleanup really.
 |(This is on top of my arithmetic patch but it should not really
 |interfere, .. in case linenumber shifts are seen.)
 ...
 |From: Steffen Nurpmeso <steffen@sdaoden.eu>
 |Date: Tue, 17 Jan 2023 21:07:07 +0100
 |Subject: [PATCH] ash: Allow enabling job control without a tty in
 | non-interactive mode..
 |
 |This is a take-over of the FreeBSD bin/sh
 |
 |  commit cd60e2c67d52e1f957841af19128c7227880743a
 |  Author:     Jilles Tjoelker <jilles@FreeBSD.org>
 |  AuthorDate: 2014-09-04 21:48:33 +0000
 |  Commit:     Jilles Tjoelker <jilles@FreeBSD.org>
 |  CommitDate: 2014-09-04 21:48:33 +0000
 |
 |      sh: Allow enabling job control without a tty in non-interactive mode.
 |
 |      If no tty is available, 'set -m' is still useful to put jobs \
 |      in their own
 |      process groups.
 |
 |and makes a script of
 |
 |  #!/bin/bash
 |  #!/tmp/busybox ash
 |  set -m
 |  (
 |  echo >&2 "inner shell has: $(ps -o pid,pgid $$ | tail -n1)"
 |  ) &
 |  echo >&2 "outer shell has: $(ps -o pid,pgid $$ | tail -n1)"
 |  echo >&2 "x is $$, job is $!: $(ps -o pid,pgid $! | tail -n1)"
 |
 |behave identical (including $(|) pipe races) when invoked in the
 |background via "./SCRIPT &".

but Herbert Xu has coded another way to achieve the same for
dash and likely soon commits it:

Herbert Xu wrote in
 <ZhJhpbIEe1RyBfk0@gondor.apana.org.au>:
 ...
 |Thanks for the patch.  I've rewritten it to minimise the impact.
 |However, the end result should be fairly similar.
 |
 |Please test this and let me know if there are any issues.

(I see none.  Maybe Ganael responds, too.)

 |
 |---8<---
 |When a tty is unavailable, or the shell is in the background,
 |job control could still be used for the purpose of setting
 |process groups.
 |
 |This is based on work by Jilles Tjoelker from FreeBSD and Steffen
 |Nurpmeso.
 |
 |Reported-by: Steffen Nurpmeso <steffen@sdaoden.eu>
 |Reported-by: Ganael Laplanche <ganael.laplanche@martymac.org>
 |Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
 |
 |diff --git a/src/jobs.c b/src/jobs.c
 |index a0f4d47..2a2fe22 100644
 |--- a/src/jobs.c
 |+++ b/src/jobs.c
 |@@ -187,11 +187,21 @@ set_curjob(struct job *jp, unsigned mode)
 | 
 | int jobctl;
 | 
 |+static void xxtcsetpgrp(pid_t pgrp)
 |+{
 |+     int fd = ttyfd;
 |+
 |+     if (fd < 0)
 |+             return;
 |+
 |+     xtcsetpgrp(fd, pgrp);
 |+}
 |+
 | void
 | setjobctl(int on)
 | {
 |+     int pgrp = -1;
 |  int fd;
 |-     int pgrp;
 | 
 |  if (on == jobctl || rootshell == 0)
 |   return;
 |@@ -207,36 +217,43 @@ setjobctl(int on)
 |   fd = savefd(fd, ofd);
 |   do { /* while we are in the background */
 |    if ((pgrp = tcgetpgrp(fd)) < 0) {
 |+close:
 |+                             close(fd);
 |+                             fd = -1;
 | out:
 |+                             if (!iflag)
 |+                                     break;
 |     sh_warnx("can't access tty; job control turned off");
 |     mflag = on = 0;
 |-                             goto close;
 |+                             return;
 |}
 |    if (pgrp == getpgrp())
 |     break;
 |+                     if (!iflag)
 |+                             goto close;
 |    killpg(0, SIGTTIN);
 |} while (1);
 |   initialpgrp = pgrp;
 |-
 |-             setsignal(SIGTSTP);
 |-             setsignal(SIGTTOU);
 |-             setsignal(SIGTTIN);
 |   pgrp = rootpid;
 |-             setpgid(0, pgrp);
 |-             xtcsetpgrp(fd, pgrp);
 |} else {
 |   /* turning job control off */
 |   fd = ttyfd;
 |   pgrp = initialpgrp;
 |-             xtcsetpgrp(fd, pgrp);
 |-             setpgid(0, pgrp);
 |-             setsignal(SIGTSTP);
 |-             setsignal(SIGTTOU);
 |-             setsignal(SIGTTIN);
 |-close:
 |-             close(fd);
 |-             fd = -1;
 |}
 |+
 |+     setsignal(SIGTSTP);
 |+     setsignal(SIGTTOU);
 |+     setsignal(SIGTTIN);
 |+     if (fd >= 0) {
 |+             setpgid(0, pgrp);
 |+             xtcsetpgrp(fd, pgrp);
 |+
 |+             if (!on) {
 |+                     close(fd);
 |+                     fd = -1;
 |+             }
 |+     }
 |+
 |  ttyfd = fd;
 |  jobctl = on;
 |}
 |@@ -391,7 +408,7 @@ restartjob(struct job *jp, int mode)
 |  jp->state = JOBRUNNING;
 |  pgid = jp->ps->pid;
 |  if (mode == FORK_FG)
 |-             xtcsetpgrp(ttyfd, pgid);
 |+             xxtcsetpgrp(pgid);
 |  killpg(pgid, SIGCONT);
 |  ps = jp->ps;
 |  i = jp->nprocs;
 |@@ -874,7 +891,7 @@ static void forkchild(struct job *jp, union node \
 |*n, int mode)
 |   /* This can fail because we are doing it in the parent also */
 |   (void)setpgid(0, pgrp);
 |   if (mode == FORK_FG)
 |-                     xtcsetpgrp(ttyfd, pgrp);
 |+                     xxtcsetpgrp(pgrp);
 |   setsignal(SIGTSTP);
 |   setsignal(SIGTTOU);
 |} else
 |@@ -1014,7 +1031,7 @@ waitforjob(struct job *jp)
 |  st = getstatus(jp);
 | #if JOBS
 |  if (jp->jobctl) {
 |-             xtcsetpgrp(ttyfd, rootpid);
 |+             xxtcsetpgrp(rootpid);
 |   /*
 |    * This is truly gross.
 |    * If we're doing job control, then we did a TIOCSPGRP which
 |-- 
 |Email: Herbert Xu <herbert@gondor.apana.org.au>
 |Home Page: http://gondor.apana.org.au/~herbert/
 |PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
 |
 --End of <ZhJhpbIEe1RyBfk0@gondor.apana.org.au>
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