file pointer while reading from txt file

Question

0.00/5 (No votes)

See more:

In my application I am reading from the text file but i need to keep eye on the file pointer where I am reading or how much content of the file i already read. and where to start next. There are TWO situations where i need to do this.

CASE 1:: While 2 system A and B are accessing the file F at the same time where A is writing and B is reading the file F. So system A need to know how much i already read and from where to read further??

CASE 2:: While System A is reading from file F1 and after analyses writing FILE F1 line description into File F2. while reading the file F1 if some specific error code detected then I need to close the file F2 and skip the ERROR LINE open new file F3 to restart the F1 analysis from ERRORLINE+1 onward.

your suggestions to handle both cases would be appreciated.
Thanks for reading with patience

Posted 27-Jan-16 22:30pm

XamBEE

Add a Solution

1 solution

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Jochen Arndt · Answer 1 · 2016-01-27T23:09:00

Just track the file position in a variable. File I/O functions return the number of items that has been read or written.

High level file I/O methods often provide functions that return the current position (e.g. ftell) than can be used too.

Special care must be taken when files are accessed by multiple processes at the same time. You should avoid to read from a file that is actually opened for writing by another process; especially when that is not only appending data but also inserting / overwriting. So you should check if your case 1 can be handled in another way.

Pseudo code for case 2:

n = 2
in = open(F1, read)
out = open(F2, create_write)
while (!end_of_file(in))
{
    line = readline(in)
    description = parseline(line)
    if (error)
    {
        close(out)
        n = n + 1
        out = open(Fn)
    }
    else
        write(out, description)
}
close(in)
close(out)