Question

I’m creating backup of my database every day.

For hard disk saving how can I delete files older than 2 weeks AND (day of month) % 14 != 0 from shell script?

So I’m looking for command like find / -mtime +14 -exec rm {} \;, with addition of not deleteting files created in 14’th or 28’th day of any month.

I’d like to have daily backups for last 2 weeks and once every 2 weeks(almost) afterwards?

PHP code in loop would be:

$mtime = filemtime($file); // Last modified date of file (created)
$day_mtime = date('j', $mtime); // Day of month (1-31)
$two_weeks_ago = time() - 60 * 60 * 24 * 14;

if ($mtime < $two_weeks_ago && $day_mtime % 14 != 0) {
    // Delete file older than 2 weeks 
    // AND not modified not 14'th nor 28'th day of month
}

Answer 1

This is the bash equivalent. A couple of point to note when moving from php to bash:

• In bash $ means “the value of…” so mtime is the variable and $mtime is the value of the variable
• The notation $(...) means run the command in the parenthesis and capture with its output
  So, $(stat -c %Y $file) is replaced with the output of stat -c %Y $file

• There can be no spaces around the assignment operators a=b works, a = b does not

  mtime=$(stat -c %Y $file)
  day_mtime=$(date -d@$mtime +%d)
  two_weeks_ago=$(date -d '2 weeks ago' +%s)
  mod_14_day=$(expr $day_mtime 14)
  if [ $mtime -lt $two_weeks_ago ] && [ $mod_14_day -eq 0 ] ; then
  fi