CODEWITHSUNDEEP
bashmacosshellterminal
tristansokol
tristansokol

Reputation: 4271

How to determine if a file has been modified recently with bash on mac

Background:

I'm trying to add something to my bash profile to see if a backup is outdated and then make a quick backup if not.

The Question

Basically I'm trying to see if a file is older than an arbitrary date. I can find the most recently updated file with 

lastbackup=$(ls -t file | head -1)

And I can get last modified date with 

stat -f "%Sm" $lastbackup

But I can't figure out how to compare that time with bash functions, or how to make a timestamp, etc.

All the other answers I found seem to use the non mac versions of stat with differently supported flags. Looking for any clues!

Upvotes: 1

Views: 2340

Answers (2)

accdias
accdias

Reputation: 5372

You can use seconds since the epoch for the actual date and the last file change and then decide if a backup is needed based on the difference of seconds.

Something like this: (edit: changed stat parameters to match OS X options)

# today in seconds since the epoch
today=$(date +%s)
# last file change in seconds since the epoch
lastchange=$(stat -f '%m' thefile)
# number of seconds between today and the last change
timedelta=$((today - lastchange))
# decide to do a backup if the timedelta is greater than
# an arbitrary number of second
# ie. 7 days (7d * 24h * 60m * 60s = 604800 seconds)
if [ $timedelta -gt 604800 ]; then
   do_backup
elif

Upvotes: 3

Terry P.
Terry P.

Reputation: 16

The find command will do what you're looking for quite nicely. Say you want to ensure you have a backup that is no older than 1 day every day (that you login), here is a test setup with two files, the find syntax, and the output you will see.

# Create a backup directory and cd to it
mkdir backups; cd backups

# Create file, oldfile and set oldfile last mod time to 2 days ago
touch file
touch -a -m -t 201801301147 oldfile

# Find files in this folder with modified time within 1 day ago;
# will only list file
find . -type f -mtime -1

# If you get no returned files from find, you know you need to run
# a backup.  You could do this (replace run-backup with your backup command):
lastbackup=$(find . -type f -mtime -1)
if [ -z "$lastbackup" ]; then
  run-backup
fi

If you view the manpage for find, look at the -atime switch for details on other units you can use (e.g. hours, minutes).

Upvotes: 0

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