Is there any way to rewrite to a .dat file created in C, without losing the previous information that was written in it?

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So far, whenever I compile a program in C that creates a file, the previous data written on it is erased in order to write the new data. As a result, I was wondering if there was a way to save the information that had already been written in the previous compilation and then add and store new data in such a file.

As a result, I was wondering if there was a way to save the information that had already been written in the previous compilation and then add and store new data in such a file.

What I have tried:

If it's possible, could you give me a simple example, please?

Posted 23-Feb-23 23:09pm

yuike

Updated 23-Feb-23 23:34pm

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CPallini · Accepted Answer · 2023-02-23T23:34:00

Solution 1

If you mean the file your C program creates, then you might open it in append mode, see fopen, fopen_s - cppreference.com[^].
On the other hand, if you mean the product(s) of the compilation process, then you should save such file(s) before compiling again (note you could automate such a task, as post-buil step).

Posted 23-Feb-23 23:34pm

CPallini

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yuike 24-Feb-23 12:28pm

Interesting. Could clarify a bit more what you mean by "the product of the compilation process", please?

CPallini 24-Feb-23 13:24pm

The major product of the compilation process is the executable file. However there are also object files and possibly assembly listing files, and linker map ones.

yuike 24-Feb-23 15:32pm

Thanks. I have another question, what are the methods to automate the task of save the file before compiling again?

CPallini 24-Feb-23 16:54pm

Usually you write a batch file for that. Such a file is then executed by your favourite IDE as post-build action (or invoked, after the build, in your makefile).

yuike 24-Feb-23 16:57pm

Thank you!

Is there any way to rewrite to a .dat file created in C, without losing the previous information that was written in it?

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Is there any way to rewrite to a .dat file created in C, without losing the previous information that was written in it?

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