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File I/O: fopen, fread, fwrite & fclose
FILE streams, text vs binary modes, error checking, and EOF
C handles file I/O through FILE* streams provided by <stdio.h>, supporting both human-readable text files and raw binary serialization.
File Stream Operations
fopen("path", "mode"): Opens a stream. Modes: "r" (read), "w" (write/truncate), "a" (append), "rb"/"wb" (binary).
Check for NULL: If a file doesn't exist or permission is denied, fopen returns NULL.
fclose(filePtr): Flushes buffers and closes the OS file descriptor.
fprintf() and fscanf(): Formatted text file I/O.
fwrite() and fread(): Fast block-level binary reads and writes directly between structs and disk.
#include <stdio.h>
int main(void) {
FILE *fp = fopen("output.txt", "w");
if (fp == NULL) {
perror("Failed to open file");
return 1;
}
fprintf(fp, "Codexia C Mastery\nVersion: %d\n", 1);
fclose(fp); // Flush and close file
return 0;
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Test Yourself With Exercise
What does `fopen()` return if the requested file cannot be opened due to missing permissions or a bad path?