UNIX for Advanced & Expert Users

I want to check the mail attachement size before sending the mail.
I coded:

Code:

IF FILESIZE > XBYTES THEN
MESSAGE "Mail attachment size exceeds limit"
ELSE
SEND MAIL.

But I want to know the quantifier.
To get the XBYTES, I used

Code:

ls -ltr filename | awk '{print $5}'

into a variable, now, if I want to check XBYTES > 15 MB, what is that I have to code ?
I coded XBYTES > 15728640
ie.1024*1024*15

I want to make sure this is right. Please let me know if I am wrong.
Also, in /etc/mail/sendmail.cf, I see

Code:

# maximum message size
#O MaxMessageSize=0

Does that mean there is no limit on message attachments/ messages ? Where could I see the limit ?

Moderator's Comments:

Use [code] and [/code] tags when posting code, data or logs etc. to preserve formatting and enhance readability, thanks.

The leading hash sign means that the lines are comment lines.
Thus the maximum size of an attachment is "unlimited" (well at least not by sendmail). Many ISPs will not allow a 15 Mb attachment.

The test in your script will obviously only work on a O/S where "ls" displays the file size in bytes.
The test in your script will only work for numbers up to 2147483647 .
((1024 x 1024 x 1024 x 2)) -1) . One byte less than 2 Gb.
This is a restriction on the maximum size of an integer in a Shell variable.