C examples for File:File Read
Demonstrates ftell() and rewind().
#include <stdlib.h> #include <stdio.h> #define BUFLEN 6/* w w w .j a v a2 s. co m*/ char msg[] = "abcdefghijklmnopqrstuvwxyz"; int main( void ) { FILE *fp; char buf[BUFLEN]; if ( (fp = fopen("TEXT.TXT", "w")) == NULL) { fprintf(stderr, "Error opening file."); exit(1); } if (fputs(msg, fp) == EOF) { fprintf(stderr, "Error writing to file."); exit(1); } fclose(fp); if ( (fp = fopen("TEXT.TXT", "r")) == NULL) { fprintf(stderr, "Error opening file."); exit(1); } printf("\nImmediately after opening, position = %ld", ftell(fp)); /* Read in 5 characters. */ fgets(buf, BUFLEN, fp); printf("\nAfter reading in %s, position = %ld", buf, ftell(fp)); /* Read in the next 5 characters. */ fgets(buf, BUFLEN, fp); printf("\n\nThe next 5 characters are %s, and position now = %ld", buf, ftell(fp)); /* Rewind the stream. */ rewind(fp); printf("\n\nAfter rewinding, the position is back at %ld", ftell(fp)); /* Read in 5 characters. */ fgets(buf, BUFLEN, fp); printf("\nand reading starts at the beginning again: %s\n", buf); fclose(fp); return 0; }