#!/bin/sh

set -ue

# Wrapper for logging to file and prepending a timestamp.
# By default writes both stdout and stderr to the log file.

usage() {
    echo "Usage: logto [-s|-e] <log_file> <command>"
    echo "Flags:"
    echo "  -s: Write only stdout to the log file."
    echo "  -e: Write only stderr to the log file."
    echo ""
    echo "Example usage:"
    echo "  logto /var/log/my.log run some command"
    exit 1
}

mode="all"

while getopts "se" opt; do
    case $opt in
        s) mode="stdout" ;;
        e) mode="stderr" ;;
        *) usage ;;
    esac
done
shift $((OPTIND-1))

if [ $# -lt 2 ]; then
    usage
fi

log_file="$1"
shift

if [ "$mode" = "stdout" ]; then
    out=$(2>/dev/null $@)
elif [ "$mode" = "stderr" ]; then
    out=$(2>&1 >/dev/null $@)
else
    out=$(2>&1 $@)
fi

if [ ! -z "$out" ]; then
    echo "$(date +"%Y-%m-%dT%H:%M:%S%z")" "$out" >>"$log_file"
fi