1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 | #include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <assert.h>
#include "clog.h"
// ftell(…) returns the position in the file where we will read or write next.
// OK to copy/adapt this function if you understand it completely.
char const* write_file(char const* contents, char const* filename) {
FILE* fp = fopen(filename, "w");
fputs(contents, fp);
fclose(fp);
return filename;
}
int main(int argc, char* argv[]) {
logf_yellow("Write \"ABC\" to file.\n");
char const* filename = write_file("ABC", __FILE__ ".txt");
logf_yellow("Open the file.\n");
FILE* fp = fopen(filename, "r");
int position_after_opening_file = ftell(fp);
log_int(position_after_opening_file);
/*
'A' 'B' 'C'
0 1 2 ftell(…) returns this just before calling fgetc(…)
*/
logf_yellow("Read file one character at a time.\n");
for(char ch = fgetc(fp); ! feof(fp); ch = fgetc(fp)) {
int position = ftell(fp);
printf("Character '%c' found at position %d.\n", ch, (position - 1));
// -1 because we called ftell(…) after we read the character.
}
logf_yellow("\nClose the file.\n");
int position_just_before_closing_file = ftell(fp);
log_int(position_just_before_closing_file);
fclose(fp);
return EXIT_SUCCESS;
}
/* vim: set tabstop=4 shiftwidth=4 fileencoding=utf-8 noexpandtab: */
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