source: vendor/bash/3.1/examples/scripts/nohup.bash

#
# BASH VERSION OF nohup COMMAND
#
ctype()
{
        path=$(builtin type -p $cmd | sed 1q)
        if [ -n "$path" ]; then
                echo "$path"
                return 0
        else
                case "$cmd" in
                */*)    [ -x "$cmd ] && { echo "$cmd" ; return 0; } ;;
                  *)    case "$(builtin type -t $cmd)" in
                        "")     return 1;;
                        *)      echo "$cmd" ; return 0;;
                        esac ;;
                esac
        fi
        return 1
}

trap '' HUP             # ignore hangup
command=$(ctype "$1")
oldmask=$(umask)
umask u=rw,og=          # default mode for nohup.out
exec 0< /dev/null       # disconnect input
if [ -t 1 ]; then       # redirect output if necessary
        if [ -w . ]; then
                echo 'Sending output to nohup.out'
                exec >> nohup.out
        else    echo "Sending output to $HOME/nohup.out"
                exec >> $HOME/nohup.out
        fi
fi

umask "$oldmask"

# direct unit 2 to a file
if [ -t 2 ]; then
        exec 2>&1
fi

# run the command
case $command in
*/*)    exec "$@"
        ;;
time)   eval "$@"
        ;;
*)      "$@"
        ;;
esac