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core/addToCrontabEveryHour.sh

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+#!/bin/bash
+
+#WARNING: Used for core functionality in setup.sh
+#         DO NOT rename the script and test changes well!
+
+
+
+# Note that an unprivileged user can use this script successfully,
+# if no user has to be added to the host because it already exists.
+function addToCrontabEveryHour() {
+    local _ROOT _MINUTE_VALUE _STRING
+    _ROOT="${0%%/core/*}/"                              #Removes longest  matching pattern '/core/*' from the end
+    ! [ -z "${2##*[!0-9]*}" ] && _MINUTE_VALUE=$((${2}%60)) # if second parameter is integer then (minute-value % 60) as safe guard
+    _STRING="${_MINUTE_VALUE:?"Missing MINUTE_VALUE"} * * * * ${1:?"Missing first parameter COMMAND"} > /dev/null 2>&1"
+    readonly _ROOT _MINUTE_VALUE _STRING
+
+    [ "$(id -u)" == "0" ] \
+        && crontab -l | grep -qF "${_STRING:?"Missing CRON_STRING"}" \
+        && echo "SUCCESS: Entry already is registered to crontab:   ("$(readlink -f ${0})")" \
+        && echo "  - '${_STRING}'" \
+        && return 0
+
+    [ "$(id -u)" == "0" ] \
+        && echo "${_ROOT:?"Missing ROOT"}" | grep "home" &> /dev/null \
+        && echo "SUCCESS: Although the entry will be skipped:       ("$(readlink -f ${0})")" \
+        && echo "  - '${_STRING}'" \
+        && echo "  that is because the current environment is:" \
+        && echo "    - ${_ROOT}" \
+        && return 0
+
+    [ "$(id -u)" == "0" ] \
+        && (crontab -l; \
+            echo "# Every hour at ?:${_MINUTE_VALUE:?"Missing MINUTE_VALUE"}:"; \
+            echo "${_STRING:?"Missing CRON_STRING"}") | crontab - \
+        && crontab -l | grep -qF "${_STRING:?"Missing CRON_STRING"}" \
+        && echo "SUCCESS: Entry is registered to crontab now:       ("$(readlink -f ${0})")" \
+        && echo "  - '${_STRING}'" \
+        && return 0
+
+    echo "FAIL: Entry could not be registered to crontab:    ("$(readlink -f ${0})")"
+    echo "  - '${_STRING:?"Missing CRON_STRING"}'"
+    echo "  - due to an error or insufficient rights."
+    return 1
+}
+
+# sanitizes all parameters
+addToCrontabEveryHour \
+    "$(echo ${1} | sed -E 's|[^a-zA-Z0-9/:@._-]*||g')" \
+    "$(echo ${2} | sed -E 's|[^a-zA-Z0-9/:@._-]*||g')" \
+    && exit 0 || exit 1