How to dynamically write to a text file in C++

Question

3.00/5 (1 vote)

See more:

Hello everyone. You know how in c++ if you use std::ofstream to otput to a file you have to refresh it every time the program executes to see any changes. So, the question is, is it possible to write to a file and kinda see in live how the contents are changing (in other words, automatically updating the file while writing to it) and how can I do it? Thank you very much in advance.

What I have tried:

std::ofstream to output to a text file.

Posted 15-Jan-19 13:07pm

Grigorii Mordkovich

Updated 16-Jan-19 8:42am

Add a Solution

3 solutions

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)

KarstenK · Answer 1 · 2019-01-15T23:12:00

The easiest way is to check the file time and when changed read the file and detect changes.

There are different tools and frameworks out, but the QFileSystemWatcher looks interesting AND portable. For Windows you may Obtaining Directory Change Notifications.

Dont ferget that its work for the operating system of the computer and so may hurt performance.

May in the written file can placed some time stamps for identification of change time. For log file deleting old content or creating files for every day is common practise.

k5054 · Answer 2 · 2019-01-15T13:25:00

Solution 1

That would depend on your OS. If you have linux or MacOS, then use tail -f. If you are on windows and have PowerShell then "Get-Content filenamehere -Wait -Tail 30" might work if you have a recent enough PowerShell version. If not google "windows tail command", and see if anything there works for you.

Posted 15-Jan-19 13:25pm

k5054

Comments

Grigorii Mordkovich 16-Jan-19 6:19am

Thank you very much. I ll try this.

Rick York · Answer 3 · 2019-01-16T08:42:00

Solution 3

Another option is to use a memory-mapped file. I know the Windows API has this and I believe is is available in Linux also.

Posted 16-Jan-19 8:42am

Rick York