Q:

Capacity of plain text file

I have a plain text file with db file extension which I am using as a disk cache.  I was wondering how much capacity a text file can have and how long it can grow?  Is there a limit? 

A:

Plaintext file limitations -
On Windows
Text files used by Notepad should be no larger than 45K. Notepad cannot open a file that exceeds 54 kilobytes (K) in size and does not allow you to continue editing a file if the file size reaches between 45K and 54K.
On Linux
Open the Terminal and then type the following command:
ulimit -a
You will see a lot of options, one of them being-
file size               (blocks, -f) 5000
This shows that the size is 5mb max. 
You can also modify the limit in Linux. 
Login as root and edit the file. 
vi /etc/security/limits.conf
Look for your username and fsize parameter.  Delete this line or set new parameter.  I am setting new file size limit to 2 GB. 
bozzmob       hard  fsize  2048000
Logout and Login, so that the changes apply on your system.