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#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/types.h>
#include <fcntl.h>
#include <sys/mman.h>
int
main(int argc, char **argv)
{
int fd, r, l;
char buf[1024];
char *v;
fd = open("/dev/zero", O_RDONLY);
if (fd < 0)
{
fprintf(stderr, "Unable to open /dev/zero for reading\n");
perror("The error was");
exit(1);
}
l = read(fd, buf, 1024);
if (l != 1024)
{
fprintf(stderr, "Asked to read 1024 bytes, got %d\n", l);
exit(1);
}
for (r=0; r<1024; r++)
if (buf[r] != 0)
{
fprintf(stderr, "/dev/zero returned a byte of %02x at offset %d\n",
buf[r], r);
exit(1);
}
l = lseek(fd, 4096, 0);
if (l != 0)
{
fprintf(stderr, "l == %d\n", l);
exit(1);
}
l = close(fd);
if (l != 0)
{
fprintf(stderr, "close: returned %d\n", l);
perror("The error was");
exit(1);
}
fd = open("/dev/zero", O_WRONLY);
if (fd < 0)
{
fprintf(stderr, "Unable to open /dev/zero for writing\n");
perror("The error was");
exit(1);
}
l = write(fd, buf, 1024);
if (l != 1024)
{
fprintf(stderr, "Asked to write 1024 bytes, got %d\n", l);
exit(1);
}
l = close(fd);
if (l != 0)
{
fprintf(stderr, "close: returned %d\n", l);
perror("The error was");
exit(1);
}
fd = open("/dev/zero", O_RDWR);
v = (char *)mmap(0, 65536, PROT_READ|PROT_WRITE, MAP_PRIVATE, fd, 0);
if (v == (char *)-1)
{
fprintf(stderr, "mmap r/w /dev/zero failed\n");
perror("The error was");
exit(1);
}
for (r=0; r<65536; r++)
if (v[r] != 0)
{
fprintf(stderr, "mmap'd r/w /dev/zero has byte %d at offset %d\n",
v[r], r);
exit(1);
}
munmap(v, 65536);
close(fd);
fd = open("/dev/zero", O_RDONLY);
v = (char *)mmap(0, 65536, PROT_READ, MAP_SHARED, fd, 0);
if (v == (char *)-1)
{
fprintf(stderr, "mmap /dev/zero r/o failed\n");
perror("The error was");
exit(1);
}
for (r=0; r<65536; r++)
if (v[r] != 0)
{
fprintf(stderr, "mmap'd r/o /dev/zero has byte %d at offset %d\n",
v[r], r);
exit(1);
}
munmap(v, 65536);
close(fd);
exit(0);
}
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