What’s the use of fopen(), fclose(), fprintf(), fscanf(), feof(), fseek(), rewind(), fread(), fwrite(), fgets(), fputs() ?

What’s the use of fopen(), fclose(), fprintf(), fscanf(), feof(), fseek(), rewind(), fread(), fwrite(), fgets(), fputs() ?

Here i use the single program to explain almost all file I/O operations simply.

#include <stdio.h>
#include <string.h>
 
int main()
{
	FILE *fp;
	char *string="This is testing for fwrite.\n";
	char buff[255];
	int n=0;

	/* File Write Operations */
	fp = fopen("test.txt", "w+");

	/* Access control flags */
	/* 
	"r" -> Open for reading.
	"w" -> Open for writing.
	"a" -> Open for appending.
	"r+" -> Both reading and writing.
	"w+" -> Both reading and writing, create new file if it exists,
	"a+" -> Open for both reading and appending.
	*/

	fprintf(fp, "This is testing for fprintf.\n");

	fputs("This is testing for fputs.\n", fp);

	fwrite(string, strlen(string),1,fp);

	fclose(fp);

	memset(buff,0x00,sizeof(buff));

	/* File Reading Operations */
	fp = fopen("test.txt", "r");

	fread(&buff,sizeof(buff),1,fp);
	printf(" fread < Read in Blocks of Array OR Structure > : ");
	printf(" \n\n test.txt \n===============================");
	printf(" \n%s===============================\n", buff );

	rewind(fp); //Reset the cursor position in file at first character
	printf("\n\n fgetc <Fetch single character> : %c\n\n", fgetc(fp) );

	fscanf(fp, "%s", buff);
	printf(" fscanf <Fetch single word starting from current position> : %s\n\n", buff );

	fgets(buff, 255, (FILE*)fp);
	printf(" fgets <Fetch whole line from current position> : %s\n", buff );

	/* Counting number of characters in file */
	fseek(fp,0L,0); // Same as rewind.
	/*
	fseek(fp, offset, position);
		Position can be
		0->start of file
		1->current position
		2->end of file
		fseek(fp,0L,1); // Stay at current position.
		fseek(fp,0L,2); // Past end of file.
		fseek(fp,m,0); // Move to (m+1) byte.
		fseek(fp,m,1) // Go forward m bytes.
		fseek(fp,-m,1); // Go backward m bytes from current position.
		fseek(fp,-m,2); // Go backward from end of file.
	*/

	while (fgetc(fp) != EOF)
			++n;
	if (feof(fp))
			printf (" feof() < Total characters > : %d\n\n",n);

	fclose(fp);

	return 0;
}

 

 

Output