117 lines
3.0 KiB
C
117 lines
3.0 KiB
C
#include <sys/types.h>
|
|
#include <sys/uio.h>
|
|
#include <fcntl.h>
|
|
#include <unistd.h>
|
|
#include <string.h>
|
|
#include <stdio.h>
|
|
|
|
int main(int argc, const char* argv[]) {
|
|
const char* file_name = "tmp.txt";
|
|
int fd, flags, mode, len;
|
|
off_t offset;
|
|
const char* write_msg = "Hello World\n";
|
|
char read_buf[128] = {0};
|
|
|
|
// write
|
|
flags = O_WRONLY | O_CREAT| O_TRUNC;
|
|
mode = 00666;
|
|
if ((fd = open(file_name, flags, mode)) < 0) {
|
|
printf("ERROR: failed to open a file for write\n");
|
|
return -1;
|
|
}
|
|
if ((len = write(fd, write_msg, strlen(write_msg))) <= 0) {
|
|
printf("ERROR: failed to write to the file\n");
|
|
return -1;
|
|
}
|
|
|
|
// lseek
|
|
if ((offset = lseek(fd, 0, SEEK_END)) != 12) {
|
|
printf("ERROR: failed to lseek the file\n");
|
|
return -1;
|
|
}
|
|
close(fd);
|
|
|
|
// read
|
|
flags = O_RDONLY;
|
|
if ((fd = open(file_name, flags)) < 0) {
|
|
printf("ERROR: failed to open a file for read\n");
|
|
return -1;
|
|
}
|
|
if ((len = read(fd, read_buf, sizeof(read_buf) - 1)) <= 0) {
|
|
printf("ERROR: failed to read from the file\n");
|
|
return -1;
|
|
}
|
|
close(fd);
|
|
|
|
if (strcmp(write_msg, read_buf) != 0) {
|
|
printf("ERROR: the message read from the file is not as it was written\n");
|
|
return -1;
|
|
}
|
|
|
|
// writev
|
|
flags = O_WRONLY | O_CREAT| O_TRUNC;
|
|
if ((fd = open(file_name, flags)) < 0) {
|
|
printf("ERROR: failed to open a file for write\n");
|
|
return -1;
|
|
}
|
|
|
|
const char* iov_msg[2] = {"hello_", "world!"};
|
|
struct iovec iov[2];
|
|
for(int i=0; i<2; ++i) {
|
|
iov[i].iov_base = (void*)iov_msg[i];
|
|
iov[i].iov_len = strlen(iov_msg[i]);
|
|
}
|
|
if ((len = writev(fd, iov, 2)) != 12) {
|
|
printf("ERROR: failed to write vectors to the file\n");
|
|
return -1;
|
|
}
|
|
|
|
// pwrite
|
|
if ((len = pwrite(fd, " ", 1, 5)) != 1) {
|
|
printf("ERROR: failed to pwrite to the file\n");
|
|
}
|
|
|
|
close(fd);
|
|
|
|
flags = O_RDONLY;
|
|
if ((fd = open(file_name, flags)) < 0) {
|
|
printf("ERROR: failed to open a file for read\n");
|
|
return -1;
|
|
}
|
|
|
|
// lseek
|
|
if ((offset = lseek(fd, 2, SEEK_SET)) != 2) {
|
|
printf("ERROR: failed to lseek the file\n");
|
|
return -1;
|
|
}
|
|
|
|
// readv
|
|
iov[0].iov_base = read_buf;
|
|
iov[0].iov_len = 3;
|
|
iov[1].iov_base = read_buf + 5;
|
|
iov[1].iov_len = 20;
|
|
if ((len = readv(fd, iov, 2)) != 10) {
|
|
printf("ERROR: failed to read vectors from the file\n");
|
|
return -1;
|
|
}
|
|
|
|
if (memcmp(read_buf, "llo", 3) != 0
|
|
|| memcmp(read_buf + 5, " world!", 7) != 0) {
|
|
printf("ERROR: the message read from the file is not as it was written\n");
|
|
return -1;
|
|
}
|
|
|
|
// pread
|
|
if ((len = pread(fd, read_buf, sizeof(read_buf) - 1, 4)) != 8) {
|
|
printf("ERROR: failed to pread from the file\n");
|
|
}
|
|
if (memcmp(read_buf, "o world!", 8) != 0) {
|
|
printf("ERROR: the message read from the file is not as it was written\n");
|
|
return -1;
|
|
}
|
|
close(fd);
|
|
|
|
printf("File write and read successfully\n");
|
|
return 0;
|
|
}
|