remove bom. usage: gcc -o nobom nobom.c && ./nobom path/to/file

nobom.c

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <stddef.h>

static char bom[3] = { 0xEF, 0xBB, 0xBF };

#define error(msg) error__(msg, __LINE__)
static int
error__(char const *msg, int line)
{
    fprintf(stderr, "Error: %s (at line %d)\n", msg, line);
    return 1;
}



int
main(int argc, char *argv[])
{
    FILE *f;
    size_t r, n;
    long size;
    char *new;
    char buf[8192];
    char path[255];
    if (argc != 2)
        return error("missing arguments");

    if ((f = fopen(argv[1], "rb")) == NULL)
        return error("fopen()");
    if ((r = fread(buf, 1, 3, f)) != 3)
        return error("fread()");

    if (memcmp(buf, bom, 3) != 0)
        return 0;

    if (fseek(f, 0, SEEK_END))
        return error("fseek()");
    if ((size = ftell(f)) == -1)
        return error("ftell()");
    if (fseek(f, 3, SEEK_SET))
        return error("fseek()");
    size -= 3;

    if ((new = malloc(size + 1)) == NULL)
        return error("malloc()");

    n = 0;
    while ((r = fread(buf, 1, 8192, f)) > 0)
        memcpy(new + n, buf, r), n += r;
    if (fclose(f))
        return error("fclose()");

    if ((f = fopen(argv[1], "w")) == NULL)
        return error("fopen()");
    if (fwrite(new, 1, size, f) != size)
        return error("fwrite()");
    if (fclose(f))
        return error("fclose()");

    return 0;
}