Send mail when no more disk space left (msmtp)

gistfile1.txt

#!/bin/bash
# Purpose: Monitor Linux disk space and send an email alert to $ADMIN
DIRNAME=$(dirname "$0")

ALERT=90 # alert level
ADMIN="[email protected]"

MAIL_CONTENT="Subject:[$(uname -n)] No more space left\\r\\n"

df -H | grep -vE '^Filesystem|tmpfs|cdrom|udev|efivars' | awk '{ print $5 " " $1 }' | {
  while read -r OUTPUT;
  do
    USED=$(echo "$OUTPUT" | awk '{ print $1}' | cut -d'%' -f1 )
    PARTITION=$(echo "$OUTPUT" | awk '{ print $2 }' )
    LOCKNAME=$(echo $PARTITION | tr / _);

    if [ $USED -ge $ALERT ]; then
      if test -f "$DIRNAME/$LOCKNAME.lock";
        then echo "Found lockfile for $PARTITION";
      else
        touch "$DIRNAME/$LOCKNAME.lock"
        echo "No more space on $PARTITION ($USED%)"
        ALERT_TEXT="- No more space left on $PARTITION ($USED%)\\r\\n\\r\\n"
        MAIL_CONTENT="${MAIL_CONTENT}${ALERT_TEXT}"
      fi
    else
      if test -f "$DIRNAME/$LOCKNAME.lock"; then rm "$DIRNAME/$LOCKNAME.lock"
    fi
  fi
  done

  echo -e $MAIL_CONTENT | msmtp $ADMIN
}