#!/bin/bash
# -*-shell-script-*-

# Executes a command in parallel or serial on a cluster.
# Copyright (C) 2002  Ernest N. Mamikonyan
#
# This program 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 2
# of the License, or (at your option) any later version.
#
# This program 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 this program; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.


# echo always prints to stderr
echo() { builtin echo "$@" >&2; }


usage() {

    if [[ "$0" = *cp ]]; then
	declare -r help_string='Copy files throughout a cluster.'
    else declare -r help_string='Executes a command on a cluster.'
    fi

    echo "\
Usage: ${0##*/} [OPTIONS] [COMMAND]
$help_string
Defaults are shown in parentheses.

  -f FILE    specify an alternative nodes file (\`$nodes_file')
  -h         display this help message and exit
  -S         execute in serial
  -s         use ssh/scp instead of rsh/rcp
  -V         display version information and exit
"

    exit $1

}

# some initializations
shopt -s expand_aliases
if [[ "$0" = *cp ]]; then alias rsh_command='rcp "$@" "$node:$dest"'
else alias rsh_command='rsh "$node" "$@"'
fi
nodes_file=/etc/nodelist
serial=false
version=false

# parse the argument list
while getopts :f:hSsV option; do
    case $option in
    f) nodes_file="$OPTARG";;
    h) usage 0;;
    S) serial=true;;
    s) [[ "$0" = *cp ]] && alias rcp=scp || alias rsh=ssh;;
    V) version=true;;
    :) echo "The \`-$OPTARG' option requires an argument!"; usage 1;;
    *) echo "\`-$OPTARG' is not a valid option!"; usage 1;;
    esac
done

shift $((OPTIND-1))

# read in the list of nodes
if [[ -f "$nodes_file" ]]; then declare -ar nodes=($(< "$nodes_file"))
else
    echo ${0##*/}: please define the list of nodes and try again
    usage 1
fi

if $version; then
    echo -n "\
psh/pcp version 1.1, Copyright © 2002  Ernest N. Mamikonyan.
psh comes with ABSOLUTELY NO WARRANTY.
This is free software, and you are welcome to redistribute it
under certain conditions; see the source for details.

The following "
    if ((${#nodes[@]} > 1)); then echo -n ${#nodes[@]} nodes are
    else echo -n node is
    fi
    echo ' defined:'
    while ((i < ${#nodes[@]})); do echo "$((++i)): ${nodes[i-1]}"; done
    exit
fi

if [[ "$0" = *cp && $# -gt 1 ]]; then
    # save the last argument (the destination)
    eval dest="\${$#}"
    # make . mean PWD
    [[ "$dest" = .{,.}{,/*} ]] && dest="$PWD/$dest"
    # copy the rest into a temp array
    for ((i=1; i<$#; ++i)); do eval args[i]="\${$i}"; done
    # now, clear the whole list and restore everything but the last argument
    shift $#; set -- "${args[@]}"
fi

if $serial; then
    [[ "$0" = *cp ]] && message='Copying to' || message='Executing on'
    for node in "${nodes[@]}"; do
	echo -en "$message $node: \e[K"
	error=$(rsh_command 2>&1)
	[[ "$error" ]] && echo "$error" || echo -n $'done\r'
    done
    echo
else
    trap 'rm -f "${temp_files[@]}"' EXIT INT TERM
    for node in "${nodes[@]}"; do
	log=$(mktemp "/tmp/${0##*/}.XXXXXX") || exit 1
	temp_files=("${temp_files[@]}" "$log")
	rsh_command &> "$log" &
    done
    wait
    for ((i=0; i<${#temp_files[@]}; ++i)); do
	error=$(< "${temp_files[i]}")
	[[ "$error" ]] && echo "${nodes[i]}: $error"
    done
fi