Script to list all cron events on a system - found on stackoverflow.com: http://bit.ly/nkFwD9 Modified from original to pick up users also in /home.

cronlist.sh

#!/bin/bash

# System-wide crontab file and cron job directory. Change these for your system.
CRONTAB='/etc/crontab'
CRONDIR='/etc/cron.d'

# Single tab character. Annoyingly necessary.
tab=$(echo -en "\t")

# Given a stream of crontab lines, exclude non-cron job lines, replace
# whitespace characters with a single space, and remove any spaces from the
# beginning of each line.
function clean_cron_lines() {
    while read line ; do
        echo "${line}" |
            egrep --invert-match '^($|\s*#|\s*[[:alnum:]_]+=)' |
            sed --regexp-extended "s/\s+/ /g" |
            sed --regexp-extended "s/^ //"
    done;
}

# Given a stream of cleaned crontab lines, echo any that don't include the
# run-parts command, and for those that do, show each job file in the run-parts
# directory as if it were scheduled explicitly.
function lookup_run_parts() {
    while read line ; do
        match=$(echo "${line}" | egrep -o 'run-parts (-{1,2}\S+ )*\S+')

        if [[ -z "${match}" ]] ; then
            echo "${line}"
        else
            cron_fields=$(echo "${line}" | cut -f1-6 -d' ')
            cron_job_dir=$(echo  "${match}" | awk '{print $NF}')

            if [[ -d "${cron_job_dir}" ]] ; then
                for cron_job_file in "${cron_job_dir}"/* ; do  # */ <not a comment>
                    [[ -f "${cron_job_file}" ]] && echo "${cron_fields} ${cron_job_file}"
                done
            fi
        fi
    done;
}

# Temporary file for crontab lines.
temp=$(mktemp) || exit 1

# Add all of the jobs from the system-wide crontab file.
cat "${CRONTAB}" | clean_cron_lines | lookup_run_parts >"${temp}" 

# Add all of the jobs from the system-wide cron directory.
cat "${CRONDIR}"/* | clean_cron_lines >>"${temp}"  # */ <not a comment>

# Add each user's crontab (if it exists). Insert the user's name between the
# five time fields and the command.
while read user ; do
    crontab -l -u "${user}" 2>/dev/null |
        clean_cron_lines |
        sed --regexp-extended "s/^((\S+ +){5})(.+)$/\1${user} \3/" >>"${temp}"
done < <((cut --fields=1 --delimiter=: /etc/passwd && find /home/ -maxdepth 1 -mindepth 1 -type d -printf "%f\n") | sort | uniq)

# Output the collected crontab lines. Replace the single spaces between the
# fields with tab characters, sort the lines by hour and minute, insert the
# header line, and format the results as a table.
cat "${temp}" |
    sed --regexp-extended "s/^(\S+) +(\S+) +(\S+) +(\S+) +(\S+) +(\S+) +(.*)$/\1\t\2\t\3\t\4\t\5\t\6\t\7/" |
    sort --numeric-sort --field-separator="${tab}" --key=2,1 |
    sed "1i\mi\th\td\tm\tw\tuser\tcommand" |
    column -s"${tab}" -t

rm --force "${temp}"

We should expand this to include /etc/anacrontab in addition to the default /etc/crontab

What I did was this:

`CRONTAB='/etc/crontab /etc/anacrontab'

and then I removed the quotes and routed any errors to null (to hide missing files)

cat ${CRONTAB} 2>/dev/null | clean_cron_lines | lookup_run_parts >"${temp}"

actually this may not be enough, I still do not see results for weekly or monthly
apparently my default /etc/anacrontab in centos contains different columns which will need more code to handle

period in days delay in minutes job-identifier command

there are also many other files this script fails to handle
ls /etc/cron.* is far more then just cron.d

Try to add this code for weekly, monthly, etc. scripts, before "Output the collected crontab lines".
The run time assigned for each job is an aproximation extracted from https://www.centos.org/docs/5/html/5.2/Deployment_Guide/s2-autotasks-cron-configuring.html ... and can vary from one system to another.

# Hourly, Daily, Weekly and Monthly scripts
CRONDIR_HOURLY='/etc/cron.hourly'
CRONDIR_DAILY='/etc/cron.daily'
CRONDIR_WEEKLY='/etc/cron.weekly'
CRONDIR_MONTHLY='/etc/cron.monthly'

ls -lR "${CRONDIR_HOURLY}" | grep "^-" | awk -v dir="${CRONDIR_HOURLY}" {'print "01 * * * * root "dir"/" $9'} >>"${temp}"
ls -lR "${CRONDIR_DAILY}" | grep "^-" | awk -v dir="${CRONDIR_DAILY}" {'print "02 4 * * * root "dir"/" $9'} >>"${temp}"
ls -lR "${CRONDIR_WEEKLY}" | grep "^-" | awk -v dir="${CRONDIR_WEEKLY}" {'print "22 4 * * 0 root "dir"/" $9'} >>"${temp}"
ls -lR "${CRONDIR_MONTHLY}" | grep "^-" | awk -v dir="${CRONDIR_MONTHLY}" {'print "42 4 1 * * root "dir"/" $9'} >>"${temp}"

We should expand this to include /etc/anacrontab in addition to the default /etc/crontab

What I did was this:

`CRONTAB='/etc/crontab /etc/anacrontab'

and then I removed the quotes and routed any errors to null (to hide missing files)

cat ${CRONTAB} 2>/dev/null | clean_cron_lines | lookup_run_parts >"${temp}"

actually this may not be enough, I still do not see results for weekly or monthly

You should modify lookup_run_parts to correctly parse anacron entries. From my fork:

# sames as lookup_run_parts, but 5 fields, not 6
function lookup_anacron_parts() {
    while read line ; do
        match=$(echo "${line}" | egrep -o 'run-parts (-{1,2}\S+ )*\S+')

        if [[ -z "${match}" ]] ; then
            echo "${line}"
        else
            cron_fields=$(echo "${line}" | cut -f1-5 -d' ')
            cron_job_dir=$(echo  "${match}" | awk '{print $NF}')

            if [[ -d "${cron_job_dir}" ]] ; then
                for cron_job_file in "${cron_job_dir}"/* ; do  # */ <not a comment>
                    [[ -f "${cron_job_file}" ]] && echo "${cron_fields} ${cron_job_file}"
                done
            fi
        fi
    done;
}