From: peter@Starbase.NeoSoft.COM (Peter da Silva)
Newsgroups: alt.sources
Subject: detach -- nohup on steroids
Date: 11 Oct 1994 13:20:37 -0500
Organization: NeoSoft Internet Services   +1 713 684 5969

After several requests, here's my detach job program. It works pretty
much anywhere that has a concept of process groups.

# This is a shell archive.  Save it in a file, remove anything before
# this line, and then unpack it by entering "sh file".  Note, it may
# create directories; files and directories will be owned by you and
# have default permissions.
#
# This archive contains:
#
#	Makefile
#	detach.1
#	detach.c
#
echo x - Makefile
sed 's/^X//' >Makefile << 'END-of-Makefile'
X# standard defines
XSHELL=/bin/sh
XCFLAGS=-O
XSHARFILES=Makefile $(MISC) $(CFILES)
XSHAR=$(TARGET).shar
X
X# program dependent defines
XOFILES=detach.o
XCFILES=detach.c
XTARGET=detach
XMISC=detach.1
X
Xdefault: $(TARGET)
X
Xall: $(TARGET) shar
X
Xshar: $(SHAR)
X
X$(TARGET): $(OFILES)
X	$(CC) $(CFLAGS) $(OFILES) -o $(TARGET)
X
X$(SHAR): $(SHARFILES)
X	shar >$(SHAR) $(SHARFILES)
END-of-Makefile
echo x - detach.1
sed 's/^X//' >detach.1 << 'END-of-detach.1'
X.TH DETACH 1
X.SH NAME
Xdetach -- when it absolutely has to run!
X.SH USAGE
X.B detach
X[
X.B -av
X]
X[
X.B -f
X.I filename
X]
X.I command
X.I args-and-options
X.SH DESCRIPTION
XThere are rude programs out there that *insist* on knowing when you've
Xhit interrupt or logged out. They don't care that you've backgrounded
Xthem and nohupped them... as soon as that signal comes in, they're
Xgone.
X.PP
XAlso, sometimes you have a background process run amok. You don't have
Xtime to look it up, because it's printing junk all over your screen.
XYou have to 'kill -9 0'... but there's another background job there that you don't want to kill.
X.PP
XWell, there is a solution... 
Xa little program called 'detach'. Detach is really dumb,
Xbut it does its job. What it does is run a command in a whole new
Xprocess group. Once you have detached a process, you can airmail
Xyour terminal to Brazil. It won't care. It'll just print its process group ID
X(suitable for feeding into kill) like the last flash of light as it vanishes
Xinto a black hole.
X.PP
XSo, when you're going to background that 80 hour build, detach it.
X.SH OPTIONS
X.IP -a
XAppend to the log file rather than overwriting it.
X.IP -v
XPrint the command being executed as well as the PID.
X.IP "-f \fBfilename\fR"
XUse the named file for the detached job's output other than "detach.out".
X.SH NOTES
XIt uses setpgrp(0) to create a new process group. I have not found any
Xsystem for which this doesn't work, but there's always a first time.
END-of-detach.1
echo x - detach.c
sed 's/^X//' >detach.c << 'END-of-detach.c'
X#include <stdio.h>
X#include <fcntl.h>
X
Xmain(ac, av)
Xint ac;
Xchar **av;
X{
X	int pid;
X	char *file;
X	int vflag;
X	int mode;
X
X	close(0); open("/dev/null", 0);
X	close(1);
X
X	file = "detach.out";
X	mode = O_TRUNC;
X	vflag = 0;
X
X	while(**++av == '-') {
X		while(*++*av) {
X			switch(**av) {
X				case 'f':
X					if(*++*av)
X						file = *av;
X					else
X						file = *++av;
X					goto next_arg;
X				case 'v':
X					vflag++;
X					break;
X				case 'a':
X					mode = O_APPEND;
X					break;
X			}
X		}
Xnext_arg:	;
X	}
X
X	if(open(file, O_WRONLY|mode|O_CREAT, 0666) < 0) {
X		perror(file);
X		exit(1);
X	}
X
X	switch(pid = fork()) {
X		case -1:
X			perror(av[0]);
X			exit(1);
X			break;
X		case 0:
X			if(vflag) {
X				char **p = av;
X
X				printf("# %d", getpid());
X				while(*p)
X					printf(" %s", *p++);
X				putchar('\n');
X			}
X			fflush(stdout);
X			close(2); dup(1);
X			setpgrp();
X			execv(av[0], av);
X			execvp(av[0], av);
X			perror(av[0]);
X			exit(1);
X			break;
X		default:
X			if(vflag) {
X				fprintf(stderr, "# %d", pid);
X				while(*av)
X					fprintf(stderr, " %s", *av++);
X				fputc('\n', stderr);
X			} else
X				fprintf(stderr, "%d\n", pid);
X			break;
X	}
X}
END-of-detach.c
exit

-- 
You summoned forth an Ancient Evil and you don't know what to do with it?