#!/bin/ksh
# @(#) dissociate.ksh 1.1 95/06/17
# 92/09/15 John H. DuBois III (john@armory.com)
# 95/06/17 Added fioe option.

name=${0##*/}
Usage=\
"Usage: $name [-hp] [-f<filename>] [-i<input-file>] [-o<output-file>]
       [-e<error-file>] command arg ..."
PrintPID=false
file=/dev/null
input= output= error=

while getopts :hpf:i:o:e: opt; do
    case $opt in
    h)
	echo \
"$name: execute a process disconnected from any tty.
$Usage
command is executed with /dev/null opened for standard input, output, and
error.  It will initially belong to its own process group with no controlling
tty.  The command is executed asynchronously, so it will not be waited for.
Its parent will be process 1 (init).
A check is done to make sure that command is executable.
Any other errors that prevent command from being executed will not be
reported, since they will occur after error output has been redirected.
Options:
-f<filename>: Open <filename> for the standard input, output, and error files.
-[ioe]<filename>: Open the given file for standard input, output, or error.
    These assignments override a filename given with -f.
-h: print this help.
-p: print the process ID of the executed command."
	exit 0
	;;
    f)
	file=$OPTARG
	;;
    i)
	input=$OPTARG
	;;
    o)
	output=$OPTARG
	;;
    e)
	error=$OPTARG
	;;
    p)
	PrintPID=true
	;;
    +?)
	print -u2 "$name: options should not be preceded by a '+'."
	exit 1
	;;
    :) 
	print -r -u2 -- \
	"$name: Option '$OPTARG' requires a value.  Use -h for help."
	exit 1
	;;
    ?) 
	print -u2 "$name: $OPTARG: bad option.  Use -h for help."
	exit 1
	;;
    esac
done
 
# remove args that were options
let OPTIND=OPTIND-1
shift $OPTIND

if [ $# -lt 1 ]; then
    print -u2 "$Usage\nUse -h for help."
    exit 1
fi

if type "$1" > /dev/null; then :; else
    echo "$name: Cannot execute $1.  Aborting." 1>&2
    exit 1
fi

[ -z "$input" ] && input=$file
[ -z "$output" ] && output=$file
[ -z "$error" ] && error=$file

/bin/setpgrp "$@" <"$input" >"$output" 2>"$error" &
$PrintPID && echo $!