new `jobid' loadable builtin like ash-based shells; fix for nofork command substitution when followed by an asynchronous subshell using GNU nohup; fix for nofork command substitution to move the file descriptor moved to the anonymous file out of the user-accessible range

examples/loadables/Makefile.in

@@ -103,7 +103,7 @@ INC = -I. -I.. -I$(topdir) -I$(topdir)/lib -I$(topdir)/builtins -I${srcdir} \
 ALLPROG = print truefalse sleep finfo logname basename dirname fdflags \
 	  tty pathchk tee head mkdir rmdir mkfifo mktemp printenv id whoami \
 	  uname sync push ln unlink realpath strftime mypid setpgid seq rm \
-	  accept csv dsv cut stat getconf kv strptime chmod fltexpr
+	  accept csv dsv cut stat getconf kv strptime chmod fltexpr jobid
 OTHERPROG = necho hello cat pushd asort
 
 SUBDIRS = perl
@@ -256,6 +256,9 @@ asort:	asort.o
 fltexpr:	fltexpr.o
 	$(SHOBJ_LD) $(SHOBJ_LDFLAGS) $(SHOBJ_XLDFLAGS) -o $@ fltexpr.o $(SHOBJ_LIBS) -lm
 
+jobid:	jobid.o
+	$(SHOBJ_LD) $(SHOBJ_LDFLAGS) $(SHOBJ_XLDFLAGS) -o $@ jobid.o $(SHOBJ_LIBS)
+
 
 # pushd is a special case.  We use the same source that the builtin version
 # uses, with special compilation options.
@@ -322,7 +325,7 @@ OBJS = print.o truefalse.o accept.o sleep.o finfo.o getconf.o logname.o \
        basename.o dirname.o tty.o pathchk.o tee.o head.o rmdir.o necho.o \
        hello.o cat.o csv.o dsv.o kv.o cut.o printenv.o id.o whoami.o uname.o \
        sync.o push.o mkdir.o mktemp.o realpath.o strftime.o setpgid.o stat.o \
-       fdflags.o seq.o asort.o strptime.o chmod.o
+       fdflags.o seq.o asort.o strptime.o chmod.o fltexpr.o jobid.o
 
 ${OBJS}:	${BUILD_DIR}/config.h
 
@@ -364,3 +367,5 @@ fdflags.o: fdflags.c
 seq.o: seq.c
 asort.o: asort.c
 strptime.o: strptime.c
+fltexpr.o: fltexpr.c
+jobid.o: jobid.c

examples/loadables/jobid.c

@@ -0,0 +1,196 @@
+/* See Makefile for compilation details. */
+
+/*
+   Copyright (C) 2026 Free Software Foundation, Inc.
+
+   This file is part of GNU Bash.
+   Bash is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.
+
+   Bash is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with Bash.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include <config.h>
+
+#include "bashtypes.h"
+#include <signal.h>
+
+#if defined (HAVE_UNISTD_H)
+#  include <unistd.h>
+#endif
+
+#include <stdio.h>
+
+#include "loadables.h"
+#include "jobs.h"
+#include "execute_cmd.h"
+
+static void
+printprocs (int job)
+{
+  PROCESS *p;
+
+  p = jobs[job]->pipe;
+  do
+    {
+      printf ("%ld", (long)p->pid);
+      p = p->next;
+      putchar (p == jobs[job]->pipe ? '\n' : ' ');
+    }
+  while (p != jobs[job]->pipe);
+}
+
+static int
+printinfo (int job, int pgrp, int jobid, int lproc)
+{
+  if (pgrp)
+    {
+      printf ("%ld\n", (long)jobs[job]->pgrp);
+      return (jobs[job]->pgrp == shell_pgrp);
+    }
+  else if (jobid)		/* caller validates job */
+    {
+      printf ("%%%d\n", job + 1);
+      return 0;
+    }
+  else if (lproc)
+    {
+      PROCESS *p;
+
+      for (p = jobs[job]->pipe; p->next != jobs[job]->pipe; p = p->next)
+        ;
+      printf ("%ld\n", (long)p->pid);
+      return 0;
+    }
+  else
+    printprocs (job);
+  return 0;
+}
+
+int
+jobid_builtin (WORD_LIST *list)
+{
+  WORD_LIST *l;
+  int any_failed, opt, job, alljobs;
+  int pgrp, jobid, lproc;
+  sigset_t set, oset;
+
+  pgrp = jobid = lproc = alljobs = 0;
+  reset_internal_getopt ();
+  while ((opt = internal_getopt (list, "agjp")) != -1)
+    {
+      switch (opt)
+	{
+	  case 'a': alljobs = 1; break;
+	  case 'g': pgrp = 1; break;
+	  case 'j': jobid = 1 ; break;
+	  case 'p': lproc = 1; break;
+	  CASE_HELPOPT;
+	  default:
+	    builtin_usage ();
+	    return (EX_USAGE);
+	}
+    }
+
+  list = loptend;
+  if ((pgrp + jobid + lproc) > 1)
+    {
+      builtin_usage ();
+      return (EX_USAGE);
+    }
+
+  any_failed = 0;
+
+  /* The -a option means all jobs; JOBSPEC arguments ignored */
+  if (alljobs)
+    {
+      if (jobs == 0)
+	return 0;
+      BLOCK_CHILD (set, oset);
+      for (job = 0; job < js.j_jobslots; job++)
+	{
+	  if (INVALID_JOB (job))
+	    continue;
+	  any_failed += printinfo (job, pgrp, jobid, lproc);
+	}
+      UNBLOCK_CHILD (oset);
+      return (sh_chkwrite (any_failed ? EXECUTION_FAILURE : EXECUTION_SUCCESS));
+    }
+
+  /* No JOBSPECs means current job */
+  if (list == 0)
+    {
+      BLOCK_CHILD (set, oset);
+      job = get_job_spec (list);	/* current job */
+      if ((job == NO_JOB) || jobs == 0 || INVALID_JOB (job))
+	{
+	  sh_badjob ("%%");
+	  any_failed++;
+	}
+      else
+	any_failed = printinfo (job, pgrp, jobid, lproc);
+      UNBLOCK_CHILD (oset);
+      return (sh_chkwrite (any_failed ? EXECUTION_FAILURE : EXECUTION_SUCCESS));
+    }
+
+  /* Otherwise we print info about each JOBSPEC argument */
+  BLOCK_CHILD (set, oset);
+  for (l = list; l; l = l->next)
+    {
+      job = get_job_spec (l);
+      if ((job == NO_JOB) || jobs == 0 || INVALID_JOB (job))
+	{
+	  sh_badjob (l->word->word);
+	  any_failed++;
+	}
+      else
+        any_failed += printinfo (job, pgrp, jobid, lproc);
+    }
+  UNBLOCK_CHILD (oset);
+
+  return (sh_chkwrite (any_failed ? EXECUTION_FAILURE : EXECUTION_SUCCESS));
+}
+
+char *jobid_doc[] = {
+	"Print information about each JOBSPEC.",
+	"",
+	"JOBSPEC is any string that can be used to refer to a job. If JOBSPEC",
+	"is omitted, use the current job.",
+	"",
+	"With no options, print the process IDs of the processes in each",
+	"JOBSPEC on a single line.",
+	"",
+	"The '-a' option prints information about each job, and any JOBSPEC",
+	"arguments are ignored.",
+	"",
+	"The '-g' option prints the process group for each JOBSPEC. The 'j' option",
+	"prints the job identifier for each JOBSPEC using \"%N\" notation, where",
+	"N is the job number. The 'p' option prints the process ID of the job's",
+	"process group leader (often the same as 'g'). Only one of these three",
+	"options may be used at a time.",
+	"",
+	"The return value is 2 if an invalid option was supplied, or more than",
+	"one valid option was supplied; 1 if the 'g' option is supplied and one of",
+	"the jobs is not in a separate process group; and 0 otherwise.",
+	(char *)NULL
+};
+
+/* The standard structure describing a builtin command.  bash keeps an array
+   of these structures.  The flags must include BUILTIN_ENABLED so the
+   builtin can be used. */
+struct builtin jobid_struct = {
+	"jobid",		/* builtin name */
+	jobid_builtin,		/* function implementing the builtin */
+	BUILTIN_ENABLED,	/* initial flags for builtin */
+	jobid_doc,		/* array of long documentation strings. */
+	"jobid [-a] [-g|-j|-p] [jobspec...]",	/* usage synopsis; becomes short_doc */
+	0			/* reserved for internal use */
+};

examples/scripts/nohup.sh

@@ -0,0 +1,12 @@
+(
+	if [ -t 1 ]; then
+		exec 1>>nohup.out || exec 1>>~/nohup.out
+	fi
+	if [ -t 2 ]; then
+		exec 2>&1
+	fi
+
+	trap '' SIGHUP
+
+	exec "$@"
+)