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scitas-motd-update
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Sat, Apr 27, 17:20

scitas-motd-update
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#!/bin/bash
### Global variables
APPNAME="$(basename ${0})"
PID="${$}"
### Functions
# Logging template
log() { echo "$(date) $(hostname -s) ${APPNAME}[${PID}]: ${1}" > /dev/${2:-stdout}; }
### locking wizardry taken from https://gist.github.com/przemoc/571091
## Copyright (C) 2009 Przemyslaw Pawelczyk <przemoc@gmail.com>
## License: GNU General Public License v2, v3
#
# Lockable script boilerplate
### HEADER ###
if [ -w /var/lock ]
then
LOCKFILE="/var/lock/`basename $0`"
else
LOCKFILE="/tmp/`basename $0`.lock"
fi
LOCKFD=99
# PRIVATE
_lock() { flock -$1 $LOCKFD; }
_no_more_locking() { _lock u; _lock xn && rm -f $LOCKFILE; }
_prepare_locking() { eval "exec $LOCKFD>\"$LOCKFILE\""; trap _no_more_locking EXIT; }
# ON START
_prepare_locking
# PUBLIC
exlock_now() { _lock xn; } # obtain an exclusive lock immediately or fail
exlock() { _lock x; } # obtain an exclusive lock
shlock() { _lock s; } # obtain a shared lock
unlock() { _lock u; } # drop a lock
### BEGIN OF SCRIPT ###
# Simplest example is avoiding running multiple instances of script.
if ! exlock_now
then
log "failed to aquire lock. Exiting!"
exit 1
fi
# Remember! Lock file is removed when one of the scripts exits and it is
# the only script holding the lock or lock is not acquired at all.
### End of locking wizardry
# Location of the configuration file
SMOTD_CONFIG=${SMOTD_CONFIG:-/etc/scitas-motd.conf}
# Read configuration options
if [ -r ${SMOTD_CONFIG} ]
then
. ${SMOTD_CONFIG}
fi
# Check that all the required configuration options are set
REQUIRED_OPTIONS="SMOTD_URL"
MISSING_OPTION=false
for option in ${REQUIRED_OPTIONS}
do
if [ ! -v ${option} ]
then
log "[ERROR] Missing configuration value: '${option}'" stderr
MISSING_OPTION=true
fi
done
if ${MISSING_OPTION}
then
log "[ERROR] Missing configuration options, update ${SMOTD_CONFIG}" stderr
exit 1
fi
# Set every other option to the defaults
SMOTD=${SMOTD:-/etc/motd.scitas}
SMOTD_CURL=${SMOTD_CURL:-curl}
SMOTD_CURL_OPT=${SMOTD_CURL_OPT:-"--location --fail --silent --max-time 30"}
SMOTD_CURL_SUFFIX=${SMOTD_CURL_SUFFIX}
SMOTD_WORKDIR=${SMOTD_WORKDIR:-/var/run/scitas-motd}
# Check if curl is available
${SMOTD_CURL} --version 2>&1 > /dev/null
if [ ! $? ]
then
log "[ERROR] curl (${SMOTD_CURL}) not available!" stderr
exit 1
fi
# Getting the list of basenames for the fragments
rm -f "${SMOTD_WORKDIR}/fragments"
mkdir -p ${SMOTD_WORKDIR}
${SMOTD_CURL} ${SMOTD_CURL_OPT} \
"${SMOTD_URL}/fragments${SMOTD_CURL_SUFFIX}" \
--output "${SMOTD_WORKDIR}/fragments" 2>&1 > /dev/null
if [ ! $? ]
then
log "[ERROR] Failed to get the fragments list from: ${SMOTD_URL}" stderr
exit 1
fi
# Getting the fragments, all the listed fragments listed are mandatory
while read frag
do
FOUND=false
# from general to more specific, more specific wins
for suffix in '' ".${SMOTD_CLUSTER}" ".$(hostname -s)"
do
${SMOTD_CURL} ${SMOTD_CURL_OPT} \
"${SMOTD_URL}/${frag}${suffix}${SMOTD_CURL_SUFFIX}" \
--output "${SMOTD_WORKDIR}/${frag}" 2>&1 > /dev/null \
&& FOUND=true
done
# it's ok as long as any one of the fragments is found
if ! ${FOUND}
then
log "[ERROR] Couldn't get the fragment '${frag}' from ${SMOTD_URL}" stderr
exit 1
fi
done < "${SMOTD_WORKDIR}/fragments"
currtime=$(date +%Y%m%d.%H%M%S)
tmpmotd="${SMOTD_WORKDIR}/motd.scitas.${currtime}"
rm -f "${tmpmotd}"
mkdir -p $(dirname "${tmpmotd}")
echo "###########################################################" \
>> "${tmpmotd}"
while read frag
do
cat "${SMOTD_WORKDIR}/${frag}" >> "${tmpmotd}"
echo "###########################################################" \
>> "${tmpmotd}"
done < "${SMOTD_WORKDIR}/fragments"
if ! diff --brief --new-file ${SMOTD} ${tmpmotd} > /dev/null
then
mv "${tmpmotd}" ${SMOTD}
else
rm -f "${tmpmotd}"
fi
exit 0

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