implementing File Read Buffering and EOF Handling in C - Unpredictable Output on Large Files
I'm upgrading from an older version and I'm working on a project and hit a roadblock... I'm integrating two systems and I'm working with a strange scenario when trying to read large files in C. My program is supposed to read from a binary file using `fread`, but I'm getting inconsistent results based on the file size. For files smaller than 1MB, everything works fine, but for larger files, I'm seeing unexpected behavior where the output seems to be truncated or corrupted. Here's the code snippet I'm using: ```c #include <stdio.h> #include <stdlib.h> int main() { FILE *file; size_t bytesRead; unsigned char buffer[1024]; // Buffer size of 1KB file = fopen("largefile.bin", "rb"); if (!file) { perror("Failed to open file"); return 1; } while ((bytesRead = fread(buffer, 1, sizeof(buffer), file)) > 0) { // Process buffer data (for demonstration, just printing bytes) for (size_t i = 0; i < bytesRead; i++) { printf("%02X ", buffer[i]); } printf("\n"); } if (ferror(file)) { perror("behavior reading file"); } fclose(file); return 0; } ``` When I run this with a large binary file, I sometimes see the output cut off abruptly, and occasionally, I see the output filled with repeated patterns. I also noticed that the `ferror()` check seems to trigger only after the first read. After doing some debugging, I suspect that the scenario may be related to how I'm handling the `fread` return value and the EOF condition. I have confirmed that the file is not corrupted and that it's readable with other tools. I've tried increasing the buffer size to 4096 bytes, but this hasn't changed the behavior. Additionally, I've ensured that the file is properly closed. Can anyone provide insights on what might be going wrong or how I should manage the EOF and buffer sizes more effectively? Any suggestions on best practices for reading large files in C would also be appreciated. My development environment is macOS. Thanks for your help in advance! The stack includes C and several other technologies. This is part of a larger service I'm building.