How to get time since file was last modified in seconds with bash?

Question

I need to get the time in seconds since a file was last modified. ls -l doesn't show it.

Answer 1

There is no simple command to get the time in seconds since a file was modified, but you can compute it from two pieces:

• date +%s: the current time in seconds since the Epoch
• date -r path/to/file +%s: the last modification time of the specified file in seconds since the Epoch

Use these values, you can apply simple Bash arithmetic:

lastModificationSeconds=$(date -r path/to/file +%s)
currentSeconds=$(date +%s)
((elapsedSeconds = currentSeconds - lastModificationSeconds))

You could also compute and print the elapsed seconds directly without temporary variables:

echo $(($(date +%s) - $(date -r path/to/file +%s)))

Answer 2

In BASH, use this for seconds since last modified:

 expr `date +%s` - `stat -c %Y /home/user/my_file`

Answer 3

I know the tag is Linux, but the stat -c syntax doesn't work for me on OSX. This does work...

echo $(( $(date +%s) - $(stat -f%c myfile.txt) ))

And as a function to be called with the file name:

lastmod(){
     echo "Last modified" $(( $(date +%s) - $(stat -f%c "$1") )) "seconds ago"
}