Wrapper script to implement sane logging to journald for cron jobs. Also allows errors to "bubble up" to cron for email alerts. (not working)

cronwrap.sh

#!/bin/bash
#===============================================================================
#
# Wrapper script to implement sane logging to journald for cron jobs. Also
#   allows errors to "bubble up" to cron for email alerts.
#
# Exit Codes:
#   0 - success
#   1 - failure
#
#===============================================================================
# MIT License
#
# Copyright (c) 2017 Jeremy Cliff Armstrong
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
# SOFTWARE.
#===============================================================================

_opts=`getopt -o a:e:t:h --long arguments:,executable:,identifier:,help -- "$@"`
_sn=$(basename "$0")
_sn=${_sn%%.*}

if [ $? != 0 ] ; then echo "$_sn: Failed parsing options." >&2 ; exit 1 ; fi
eval set -- "$_opts"

_help=0
while true
do
    case "$1" in
        -a | --arguments )      _ARGS="$2";     shift 2 ;;
        -e | --executable )     _EXEC="$2";     shift 2 ;;
        -t | --identifier )     _IDENT="$2";    shift 2 ;;
        -h | --help )           _help=1;        shift   ;;
        -- ) shift; break ;;
        * ) break ;;
    esac
done

if [[ _help -gt 0 ]]; then
    #    0         1         2         3         4         5         6         7         8
    #    |123456789|123456789|123456789|123456789|123456789|123456789|123456789|123456789|
    echo "$_sn: Usage"
    echo
    echo "  -a|--arguments   Specify arguments for the executable to be wrapped. If"
    echo "                   argument string contains spaces it must be enclosed in"
    echo "                   quotes."
    echo
    echo "  -e|--executable  Specify path for the executable to be wrapped. If path"
    echo "                   contains spaces it must be enclosed in quotes. REQUIRED."
    echo
    echo "  -t|--identifier  Specify a short string that is used to identify the cronjob"
    echo "                   being logged. Will be prefixed with \"cronwrap-\". REQUIRED."
    echo
    echo "  -h|--help        Displays this help message."
    echo
    exit 0
fi

# set defaults for missing required arguments or error
if [ -z ${_EXEC:+x}     ]; then echo "$_sn: -e|--executable is a required argument. Try with --help." >&2; exit 1; fi
if [ -z ${_IDENT:+x}    ]; then echo "$_sn: -t|--identifier is a required argument. Try with --help." >&2; exit 1; fi

# ensure command exists and is executable for us
if [ ! -x $_EXEC    ]; then echo "$_sn: Unable to locate executable $_EXEC. Check your path and permissions." >&2; exit 1; fi

# use a named pipe to get around race condition with journald.
_pipe=/tmp/$_IDENT.out
if [ -p $_pipe ]; then echo "$_sn: $_pipe Exisits! Either wrapper is being called too often for identifier $_IDENT or pipe is a zombie." >&2; exit 1; fi

# create pipe and hold it open with file handle
mkfifo $_pipe
systemd-cat --identifier=$_IDENT --priority="info" < $_pipe &
exec 3>$_pipe

# trap exit signal to ensure cleanup
function finish {
    exec 3>&-
    if [ -p $_pipe ]; then rm $_pipe; fi
}
trap finish EXIT

# log function to actualy write out results.
function journaldlog {
    __tmplvl="$1"
    #__msg="${@:2}"
    __msg=$(cat; echo x)
    __msg=${__msg%x}
    #echo "DEBUG journaldlog: \$1       = $__tmplvl" #debugging - deleteme
    #echo "DEBUG journaldlog: \$(cat)   = $__msg" #debugging - deleteme
    
    if [ -z ${__tmplvl:+x}  ]; then __tmplvl=4; __msg='Empty log priority and message!'; fi
    if [ -z ${__msg:+x}     ]; then __tmplvl=4; __msg='Empty log message!'; fi

    case "$__tmplvl" in
        debug | 7 )             __level='7'; __lname='DEBUG'    ;;
        info | 6 )              __level='6'; __lname='INFO'     ;;
        notice | 5 )            __level='5'; __lname='NOTICE'   ;;
        warning | warn | 4 )    __level='4'; __lname='WARNING'  ;;
        error | 3 )             __level='3'; __lname='ERROR'    ;;
        critical | 2 )          __level='2'; __lname='CRITICAL' ;;
        emergency | 1 )         __level='1'; __lname='EMERGENCY';;
        * )                 echo "$_sn: Unknown log priority $1. Exiting." >&2; exit 1;;
    esac

    # log the thing
    echo "\<$__level\> $__lname: $__msg" >&3
    #if [ "$__level" -le "4" ]; then echo "$_sn: $__lname - $__msg" >&2; fi
    echo "$_sn - $__lname: $__msg"
}

# redirect all further stdout to the log function using "info" priority level (maybe some other day)
#exec 1>journaldlog info -

# redirect all further stderr to the log function with "error" priority level (maybe some other day)
#exec 2>journaldlog error -


#do the thing - triggers only for the error invocation, passes NULL for second parameter
#(
#    exec 7>&1
#    (
#        stdbuf -oL -eL $_EXEC $_ARGS | journaldlog info
#    ) 2>&7 1>/dev/null
#) | journaldlog error

#do the thing - triggers journaldlog only twice, not line by line.
{ $_EXEC $_ARGS 2>&1 1>&7 7>&- | journaldlog error; } 7>&1 1>&2 | journaldlog info