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#include <stdio.h>
static void create_file (char const *fname, long n, int val)
{
FILE *fp = fopen(fname, "wb");
if (fp != NULL)
{
long i;
for (i = 0; i < n; i++)
{
fputc(val, fp);
}
fclose (fp), fp = NULL;
}
else
{
perror (fname);
}
}
static void dump_file (char const *fname)
{
FILE *fp = fopen(fname, "rb");
if (fp != NULL)
{
int c;
/* ultra simpliste... */
while ((c = fgetc(fp)) != EOF)
{
printf("%02X ", (unsigned)c);
}
printf ("\n");
fclose (fp), fp = NULL;
}
else
{
perror (fname);
}
}
static void modif_file (char const *fname, long ofs, int val)
{
FILE *fp = fopen(fname, "rb+");
if (fp != NULL)
{
fseek(fp, ofs, SEEK_SET);
if (!ferror(fp))
{
fputc(val, fp);
}
fclose (fp), fp = NULL;
}
else
{
perror (fname);
}
}
int main (void)
{
#define fname "data.bin"
create_file(fname, 10, 0xAA);
dump_file(fname);
modif_file (fname, 4, 0x55);
dump_file(fname);
return 0;
} |
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