Downloading gzip'd tar file from web server to update NFS automounts

gistfile1.txt

#!/bin/bash
 
# This script checks the timestamp of the fileURL and compares it against a locally
# cached timestamp. If the archive's timestamp is newer, then it gets downloaded,
# extracted into /etc/, and the automount cache gets flushed.
 
fileURL="http://server.name.here/path/to/automounts.tgz"
 
sleep 20
 
# Custom curl options
myCurl () { /usr/bin/curl --silent --show-error "$@"; }
 
# Get modification date of fileURL
modDate=$(myCurl --head $fileURL | awk -F': ' '/Last-Modified/{print $2}')
 
# update_automounts function, called only if needed
update_automounts () {
    echo $modDate > /tmp/automounts_timestamp
    myCurl --output /tmp/automounts.tgz $fileURL
    # backup the original auto_master
    if [ ! -f /etc/auto_master~orig ]; then
        cp /etc/auto_master /etc/auto_master~orig
    fi
    # untar into place
    tar zxf /tmp/automounts.tgz -C /etc
    # purge automount cache
    automount -vc && exit 0
}
 
# Compare timestamps and update automounts if needed.
if [ -f /tmp/automounts_timestamp ]; then
    cachedDate=$(cat /tmp/automounts_timestamp)
    if [ "$cachedDate" == "$modDate" ]; then
        exit 0
    else
        update_automounts
    fi
else
    update_automounts
fi