C fwrite() writes amount of characters doubled

Question

When I use this code

FILE *f = fopen(file, "wb");
fflush(f);
if (f==NULL) {
    //perror(f);
    return 0;
}
else{
    fwrite(text, sizeof(char), strlen(text), f);
    int i = fprintf(f, "%s", text);
    if (i>0) {
        fclose(f);

        return  1;
    }

(text is const char text[1024000], which is set as one of the arguments in the function) if I write

This is a test
This is a test

to test if it can write multiple lines, it writes this

This is a test
This is a testThis is a test
This is a test

why do I get this weird behavior?

score 5 · Accepted Answer · answered Mar 18 '13 at 02:49

5

You're writing twice:

fwrite(text, sizeof(char), strlen(text), f);
int i = fprintf(f, "%s", text);

Pick one

answered Mar 18 '13 at 02:49

Martin

6,632
4
25
28

score 0 · Answer 2 · answered Mar 18 '13 at 02:49

0

These two lines write "text" twice. They do same thing.

fwrite(text, sizeof(char), strlen(text), f);
int i = fprintf(f, "%s", text);

The only difference is fprintf write one more byte '\0' than fwrite.

answered Mar 18 '13 at 02:49

TieDad

9,143
5
32
58

Ha, beat you by 12 seconds ;) – Martin Mar 18 '13 at 02:50

C fwrite() writes amount of characters doubled

2 Answers2