Confusion with File I/O Buffering in C: Unexpected Data Loss When Writing to Files
Quick question that's been bugging me - I'm integrating two systems and I'm relatively new to this, so bear with me... I recently switched to I've searched everywhere and can't find a clear answer... I'm working with an scenario with file I/O in C where I'm experiencing unexpected data loss when writing to a file. I'm using `fprintf()` to write formatted data to a file, but some of the writes seem to be missing. Here's a simplified version of my code: ```c #include <stdio.h> int main() { FILE *file = fopen("output.txt", "w"); if (file == NULL) { perror("Failed to open file"); return 1; } for (int i = 0; i < 10; i++) { fprintf(file, "Line %d\n", i); if (i % 3 == 0) { fflush(file); // Manual flush every 3 writes } } fclose(file); return 0; } ``` I expect this code to write all ten lines to `output.txt`, but I noticed that sometimes not all the lines appear in the file when I open it. I’m working with GCC version 11.1 on Ubuntu 20.04. I've tried calling `fflush()` after each write, but this seems to give me a performance hit and doesn’t consistently resolve the scenario. I also checked if there are any issues with file permissions, and everything seems fine. Is there a specific scenario in C where buffered writes can cause data not to be flushed to the file, or am I missing something in my file handling? Any help would be appreciated! This is part of a larger service I'm building. Am I approaching this the right way? This is happening in both development and production on Debian. Thanks for any help you can provide! The project is a mobile app built with C. I'd be grateful for any help. I'd be grateful for any help.