Shell Programming and Scripting

I have to run a shell , only if file_a.txt is updated correctly before 1hr.

that is,

Code:

file_a.txt
2011_09_21__14:10:20  --> any format..

And

Code:

the shell can be like,
if [ (date now) - (date from file_a.txt) > 1hr ] ; then
Run some shell
update file_a.txt with (date now)
fi

how to do this ?

Some clarifying questions:

i am sorry , if you are not clear from my description.

file_a.txt contains only one line , which is updating by us. [ie; time]

It can be in any format , i prefer something like:
201109211410

OS : fedora / CentOS

---------- Post updated at 05:49 PM ---------- Previous update was at 04:33 PM ----------

I got so many scripts to get / change date format..

But not the same what i asked , hitting on my head

The format you're proposing would work. Just use date to output the date/time appropriately, and then substract from it the current time (same format), so you'd get (for example)

Code:

diff = $((201109211410 - 201109211310 ))
if [[ $diff -ge 100 ]]
then
  echo "1 hour has passed"
else
  echo "Wait a bit longer"
fi

What do you mean by "any format" because if the format changes then any script no matter how well written wont work so decide on a format and stick to it and use perl...but if you insist on the shell then a format like YYYYMMDHHMMSS is viable for time diffs.

pludi ,

But i have a doubt in this,
think about this condition,

befo_=110921232049 --> 21/09/2011 23:20:49
now_=110921233957 --> 21/09/2011 23:39:57

now_ - befo_ = 1908 [Which is > 100 !!! But just 19min only passed]

Again if we think about 1000 [ie; with Hour-Digit or 10000... ] same problem will be there.


.

---------- Post updated at 11:51 PM ---------- Previous update was at 11:47 PM ----------

Anyway,

i changed the entire logic. I am not using these things..

Made this function alone in my shell with another parameter...

Thanks.

Well, then stay consistent. In your original example, you gave the date as YYYYMMDDhhmm, so anything >= 100 would mean 1 hour has passed. Now you're using YYMMDDhhmmss, you if you apply even a tiny bit of logical thinking you'd see that 100 wouldn't fit anymore, but that you have to shift it left by 2 places!!