#!/bin/bash
#
# NAME
#   fal - wrapper script to run several concurrent commands and gather their
#   output into one log file. fal is an abbreviation for "fork, aggregate, log"
#
# SYNOPSIS
#   fal -c count [-l logfile] [-t] [-p pipe] [--] command [command_args]
#
# OPTIONS
#   -c count
#       Run command concurrently count times.
#
#   -l logfile
#       Store logs to the logfile. By default logfile is stored in current
#       directory and called the same as the command to run but with ".log"
#       extension. If such file exists, the output will be attached to the end
#       of the file.
#
#   -p pipe
#       Create named pipe for aggregating stdout of processes. By default file
#       is called command.pipe
#
#   -t
#       write output to both logfile and stdout
#
#   The command will be run in a subshell with its arguments. If for some reason
#   arguments are similar to those accepted by this script, use "--" to separate
#   fal arguments and command to be run.

print_usage()
{
    echo "Usage: $0 -c count [-l logfile] [-p pipe] [--] command [command_args]" >&2
    exit 1;
}

# Parsing arguments
if [ "$#" -lt 3 ] ; then
    print_usage;
fi

set -- `getopt "c:l:p:t" "$@"`

while [ ! -z "$1" ]
do
    case $1 in
        -c) COUNT=$2 ;;
        -l) LOG_FILENAME=$2 ;;
        -p) PIPE_FILENAME=$2 ;;
        -t) ENABLE_STDOUT=1 ;;
        --) break ;;
    esac

    shift
done

# Check variables and set default settings if needed
COMMAND_STRING=$@
COMMAND_STRING=${COMMAND_STRING#*-- }
COMMAND=${COMMAND_STRING%% *}

if [ -z "$COUNT" ] ; then
    print_usage;
fi

if [ -z "$LOG_FILENAME" ] ; then
    LOG_FILENAME="$COMMAND.log"
fi

if [ -z "$PIPE_FILENAME" ] ; then
    PIPE_FILENAME="$COMMAND.pipe"
fi

# Some debugging info before actual work.
#echo "ARGV           = $@"
#echo "COMMAND_STRING = $COMMAND_STRING"
#echo "COMMAND        = $COMMAND"
#echo "LOG_FILENAME   = $LOG_FILENAME"
#echo "PIPE_FILENAME  = $PIPE_FILENAME"
#echo "COUNT          = $COUNT"

if [ ! -p $PIPE_FILENAME ] ; then
    mkfifo $PIPE_FILENAME
fi

for ((i=1 ; i <= COUNT ; i++ ))
do
    eval $COMMAND_STRING >$PIPE_FILENAME 2>$PIPE_FILENAME &
done

# The next command will never exit until all PIDs who feed the pipe exit. After,
# command will exit with "broken pipe" message which will be suppressed.
if [ -z "$ENABLE_STDOUT" ] ; then
    cat $PIPE_FILENAME >> $LOG_FILENAME 2>/dev/null
else
    cat $PIPE_FILENAME | tee $LOG_FILENAME
fi

# Cleaning up before exit
rm $PIPE_FILENAME

exit 0;