File I/O In C

• Required library: <stdio.h>
• FILE struct is a specific pointer type held by the standard I/O library.

Reading A File

Open a file with the function: fopen(char *filename, char *mode) and read from it using fscanf, fgets. Once done, you should close the file using fclose(filePointer).

fscanf is not recommended since it has conflicts with buffer sizes and undefined behavior - same reason to not use scanf.

char *buffer = malloc(sizeof(char) * 30);
FILE *fp = open("myfile.txt", "r");

fgets(buffer, 30, fp);
fclose(fp);
free(buffer);

Writing To A File

Open a file with the function: fopen(char *filename, char *mode) and write to it using fprintf, fputs. You can flush the write buffer by running fflush(filePointer). Once done, you should close the file using fclose(filePointer).

FILE *fp = open("myfile.txt", "w");

fputs("this is a new line\n", fp);

fclose(fp);