c++ "log file"

[akio123008]

I've made a C++ program that does its job well, and I'm quite satisfied with the result, since I'm not that familiar with the language yet. It's a console application. Now here's my question: is there a nice and simple way for "dumping" all the contents of the console into a text file while the program runs?

[Pinguinsan]

The easiest way (from outside the program):

MyProgram > logfile.txt 2>&1

This will redirect all stdout (and stderr) to the file logfile.txt. If logfile.txt already exists, it will be overwritten by this command, so be careful. If you instead want to append the output to the file, use: 

MyProgram >> logfile.txt 2>&1

The 2>&1 at the end tells the shell to close stderr and instead redirect it to stdout, so that the file will get stdout and stderr. If you don't care about stderr, you can omit this part.

[akio123008]

From outside the program? do you mean in a separate command prompt?

[Mira Yurizaki]

22 minutes ago, akio123008 said:

From outside the program? do you mean in a separate command prompt?

When you launch the program, you can redirect standard output to a file as in the manner described.

 

However, this may override standard output entirely, meaning you won't see anything show up on the console.

 

EDIT: If you want the program to output to a file without mucking with command line options (because not everyone is versed enough to know that), I would suggest using the I/O library: http://www.cplusplus.com/doc/tutorial/files/

[akio123008]

20 minutes ago, M.Yurizaki said:

EDIT: If you want the program to output to a file without mucking with command line options (because not everyone is versed enough to know that), I would suggest using the I/O library: http://www.cplusplus.com/doc/tutorial/files/

Well that's a nice solution. Thank you.

[Mira Yurizaki]

2 minutes ago, akio123008 said:

Well that's a nice solution. Thank you.

As a bonus tip, if you need to log data in a table form, I highly suggest using the comma-separated value format (which saves as a .csv file). It's plain text and practically all spreadsheet programs can open it up.

[geo3]

1 hour ago, akio123008 said:

Well that's a nice solution. Thank you.

If you don't want to do it yourself you can just get a library that does logging. Such as https://github.com/emilk/loguru

[Unimportant]

4 hours ago, akio123008 said:

I've made a C++ program that does its job well, and I'm quite satisfied with the result, since I'm not that familiar with the language yet. It's a console application. Now here's my question: is there a nice and simple way for "dumping" all the contents of the console into a text file while the program runs?

If you've written the program using iostreams (std::cout) then it should be rather easy to add this functionality.

All your output operations should accept any std::ostream. So you can make a std::ostream reference and write to that rather then std::cout. Then you can assign any output stream to this reference you want, be it std::cout, a std::ofstream or some std::ostream derivative you've yet to think of and create.