If file modification date is older than N days

Question

This question pertains to taking action if a file has a modification date older than so many days. I'm sure it would be similar for creation date or access date, but for modification date, if I have:

file=path-name-to-some-file N=100  # for example, N is number of days 

How would I do:

if file modification time is older than N days then fi 

Answer 1

Several approaches are available. One is just to ask find to do the filtering for you:

if [[ $(find "$filename" -mtime +100 -print) ]]; then   echo "File $filename exists and is older than 100 days" fi 

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Another is to use GNU date to do the math:

# collect both times in seconds-since-the-epoch hundred_days_ago=$(date -d 'now - 100 days' +%s) file_time=$(date -r "$filename" +%s)  # ...and then just use integer math: if (( file_time <= hundred_days_ago )); then   echo "$filename is older than 100 days" fi 

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If you have GNU stat, you can ask for a file's timestamp in seconds-since-epoch, and do some math yourself (though this will potentially be a bit off on the boundary cases, since it's counting seconds -- and not taking into account leap days and such -- and not rounding to the beginning of a day):

file_time=$(stat --format='%Y' "$filename") current_time=$(( date +%s )) if (( file_time < ( current_time - ( 60 * 60 * 24 * 100 ) ) )); then   echo "$filename is older than 100 days" fi 

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Another option, if you need to support non-GNU platforms, is to shell out to Perl (which I'll leave it to others to demonstrate).

If you're interested more generally in getting timestamp information from files, and portability and robustness constraints surrounding same, see also BashFAQ #87.

Answer 2

I'm surprised no one mentioned this method - it's hiding right there in man test, implied by -nt and -ot, so I suspect it's been there for a long time:

N_DAYS_AGO=/tmp/n-days-ago.$$ touch -d "$N days ago" $N_DAYS_AGO if [ "$myfile" -ot "$N_DAYS_AGO" ]; then    ... fi