t_readv.c

#include <sys/stat.h>
#include <sys/uio.h>
#include <fcntl.h>
#include "tlpi_hdr.h"

int
main(int argc, char *argv[])
{
    int fd;
    struct iovec iov[3];
    struct stat myStruct;   // First buffer
    int x;                  // Second buffer
#define STR_SIZE 100
    char str[STR_SIZE];     // Third buffer
    ssize_t numRead, totRequired;

    if (argc != 2 || strcmp(argv[1], "--help") == 0)
        usageErr("%s file\n", argv[0]);

    fd = open(argv[1], O_RDONLY);
    if (fd == -1)
        errExit("open");

    totRequired = 0;

    iov[0].iov_base = &myStruct;
    iov[0].iov_len = sizeof(struct stat);
    totRequired += iov[0].iov_len;

    iov[1].iov_base = &x;
    iov[1].iov_len = sizeof(x);
    totRequired += iov[1].iov_len;

    iov[2].iov_base = str;
    iov[2].iov_len = STR_SIZE;
    totRequired += iov[2].iov_len;

    numRead = readv(fd, iov, 3);
    if (numRead == -1)
        errExit("readv");

    if (numRead < totRequired)
        printf("Read fewer bytes than requested\n");

    printf("total bytes requested: %ld; bytes read: %ld\n",
            (long) totRequired, (long) numRead);
    exit(EXIT_SUCCESS);
}