file age checking

Oinopion · 03-10-2006, 02:43 PM

Hi!
Sorry for such noob question, but how to check which of two files is newer?

Thx

rose_bud4201 · 03-10-2006, 02:45 PM

ls -l <filename> (lower-case L, not the number 1). All files get a date/timestamp when they're created, and it's updated whenever they're updated (written to).

Oinopion · 03-10-2006, 02:47 PM

Can i do it with regexp? I mean: I have two files a.txt and b.txt and want to know whether a.txt is newer (mod. time) then b.txt and then do sth with newer file. ls -l is known to me, but I don't find this much helpful in automated updater (?!?), but thx any way.

gilead · 03-10-2006, 03:00 PM

ls -lt will sort files by modification time so you could use the following to return the listing for the new file:

Code:

ls -lt a.txt b.txt | head -1

If you just want the name:

Code:

ls -lt a.txt b.txt | head -1 | awk '{ print $8}'

or

Code:

ls -lt a.txt b.txt | head -1 | cut -d' ' -f9

jschiwal · 03-10-2006, 03:03 PM

Read the "info bash" manual for more.

Quote:

`FILE1 -nt FILE2'
True if FILE1 is newer (according to modification date) than
FILE2, or if FILE1 exists and FILE2 does not.

`FILE1 -ot FILE2'
True if FILE1 is older than FILE2, or if FILE2 exists and FILE1
does not.

Oinopion · 03-10-2006, 03:11 PM

So why does in not work:

Code:

if 'a -nt b' then echo "aaa" else echo "bbb" fi;

gilead · 03-10-2006, 03:19 PM

Try the following instead:

Code:

if [ a -nt b ]; then echo "aaa"; else echo "bbb"; fi

Oinopion · 03-10-2006, 03:23 PM

Quote:

Originally Posted by gilead

Try the following instead

...)

BIG THX. Thas right what I was looking for. And I'll read man bash!

JockVSJock · 03-11-2006, 06:37 AM

I'm in the habit of using

Code:

ls -alt

all of the time...