Creating files using variables in C

Question

I have a question here that I cant find anywhere. I have been looking for the longest and my professors are useless. I'm trying to create N amount of files inside a for loop in C. I've tried the following code...and clearly that doesn't work, how do i go about make these files inside a for loop?

int i;
int N = 10;
for(i = 0; i < N; i++)
{
    fopen(("file%d",i),"w");
}

proper grammer didnt allow me to put this portion up essentially i want to make the files file0, file1, file2....etc whatever N is. — Steven R
– Steven R, Commented Jul 19, 2014 at 19:03
Are you asking how to combine ints with strings or on how to create files? Not every C function lets you use formatted string syntax like printf, check out sprintf. — Benjamin Gruenbaum
– Benjamin Gruenbaum, Commented Jul 19, 2014 at 19:05
@BenjaminGruenbaum: sprintf can be dangerous (and is becoming deprecated). Should use snprintf — Basile Starynkevitch
– Basile Starynkevitch, Commented Jul 19, 2014 at 19:15

Basile Starynkevitch · Accepted Answer · 2014-07-19 19:17:18Z

1

Try

 int i;
 const int N = 10;
 for(i = 0; i < N; i++) {
    char nambuf[32];
    snprintf (nambuf, sizeof(nambuf), "file%d", i);
    FILE* f = fopen(nambuf, "w");
    if (!f) {perror(nambuf); exit(EXIT_FAILURE);};
    // print something in f, like
    fprintf (f, "this is %s\n", nambuf);
    fclose(f);
 }

Read documentation of snprintf(3), fopen(3), fclose(3), perror(3) ...

snprintf is useful to fill a string buffer. fopen can take such a buffer. Errors could happen, so we test some of them (you should also test failure of fprintf & fclose but I am lazy for that) and use perror to report them.

Learn about asprintf and C dynamic memory allocation

edited Jul 19, 2014 at 19:17

answered Jul 19, 2014 at 19:06

Basile Starynkevitch

1

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7 Comments

Steven R Over a year ago

you are a genious!! it worked, thanks a lot. Seems like to do a simple task, takes much more lines to do in C.

Basile Starynkevitch Over a year ago

Please take time to read more books about C. Study the source code of some existing free software....

Steven R Over a year ago

Ive used all this stuff before, I just didnt think to put all of them together @gekannt and like i said, ive searched, but nothing came up like this anywhere

Basile Starynkevitch Over a year ago

@StevenR: what source code of some free software in C have you looked into?

Steven R Over a year ago

@BasileStarynkevitch i just google what im looking for, its always something very simple (thats the worst part) but if i understand your question correctly, ive looked at a lot of source code, but Ive just been brain fried past couple days, doing things in C i dont even know, I always tend to ask the very simple questions that i get stuck on. and deal with the hard problems myself

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