Segmentation fault on recover pset4

Question

My program compiles, but when I run it I get a segmentation fault and nothing else:

    ~/workspace/recover/ $ make recover
    clang -fsanitize=integer -fsanitize=undefined -ggdb3 -O0 -std=c11 -Wall 
    -Werror -Wextra -Wno-sign-compare -Wshadow    recover.c  -lcrypt -lcs50 
    -lm -o recover
    ~/workspace/recover/ $ ./recover card.raw
    Segmentation fault
    ~/workspace/recover/ $ 

Here is my code:

    #include <cs50.h>
    #include <stdio.h>
    #include <stdlib.h>
    #include <stdint.h>

    typedef uint8_t BYTE;

    int main(int argc, char *argv[])
    {
int jpg_ctr = 0;
// ensure proper usage
if (argc != 2)
{
    fprintf(stderr, "Usage: ./recover jpeg\n");
    return 1;
}

// remember filenames
char *pfile_n = argv[1];

// open input file
FILE *pfile = fopen(pfile_n, "r");
if (pfile == NULL)
{
    fprintf(stderr, "Could not open %s.\n", pfile_n);
    return 2;
}
BYTE iter[512];
FILE *jpeg = NULL;
char jpegn[16];

while (!feof(pfile))
{
    if (iter[0] == 0xff && iter[1] == 0xd8 && iter[2] == 0xff && (iter[3] & 0xf0) == 0xe0)
    {
        if (jpg_ctr > 0)
        {
            fclose(jpeg);
        }
        jpg_ctr++;
        sprintf(jpegn, "%03d.jpg", jpg_ctr);
        fwrite(iter, sizeof(iter), 1, jpeg);
        jpeg = fopen(jpegn, "w");
    }
    if (jpg_ctr > 0)
    {
        fwrite(iter, sizeof(iter), 1, jpeg);
    }
    fread(iter, sizeof(iter), 1, pfile);
}

// close infile
fclose(pfile);

// success
return 0;
}

Sorry for the poor formatting!

Answer 1

The first step is to identify which line is triggering the seg fault.

When the code writes to the output file, has the file been opened yet?

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