linux的c语言编程常用语句

for (i = 1; i < argc ;) {
if (0 == strcmp(argv[i], "-m") && (argc - i > 1)) {
tty_modem = argv[i + 1];
i += 2;
} else if (0 == strcmp(argv[i], "-p") && (argc - i > 1)) {
tty_pc = argv[i + 1];
i += 2;
} else if (0 == strcmp(argv[i], "-d") && (argc - i > 1)) {
i += 2;
} else if (0 == strcmp(argv[i], "-f") && (argc - i > 1)) {
modem_config_file = argv[i + 1];
i += 2;
} else if (0 == strcmp(argv[i], "-t") && (argc - i > 1)) {
tunnel_switch = argv[i + 1];
if (0 == strncmp(tunnel_switch, "on", 2)) {
tunnel_mode = 1;
}
i += 2;
}
}

#define AT_CMD_OK 0
#define AT_CMD_REOPEN 1
#define AT_CMD_RESEND 2

result = wait_for_data (fd, 3000 );
if (result == AT_CMD_OK ) {
if (read(fd, buf, buf_size-1) < 0) {
LOGE(TAG"Read response from %s error, error num is %d\n", tty_name, errno);
return -1;
}
} else if (result == AT_CMD_RESEND) {
poll_cnt++;
LOGD(TAG"Wait %s result, poll %s failed %d times\n", at_cmd, tty_name, poll_cnt);
sleep(2);
if (poll_cnt >= POLL_RETRY_MAX)
return -1;
} else {
LOGD(TAG"Wait %s result, poll %s failed and need reopen.\n", at_cmd, tty_name);
modem_hangup_flag = 1;
return -1;
}
int wait_for_data( int fd, long wait_time_ms)
{
    struct pollfd fds[1];
    int poll_ret;
    int retVal = AT_CMD_OK;

    fds[0].fd = fd;
    fds[0].events = POLLIN;
    fds[0].revents = 0;

    poll_ret = poll( fds, 1, wait_time_ms);
    if ( 0 < poll_ret ) {
        if ( fds[0].revents & POLLHUP ) {
            LOGE(TAG"device hung up\n");
            retVal = AT_CMD_REOPEN;
            goto Exit_Handler;

        } else if ( fds[0].revents & POLLIN ) {
            LOGV(TAG"Received response data\n");

        } else {
            /* Not sure we will ever get here */
            LOGE(TAG"Unexpected event while waiting for response\n");
            retVal = AT_CMD_RESEND;
            goto Exit_Handler;
        }
    } else if ( 0 == poll_ret ) {
        LOGE(TAG"Timed out while waiting for response\n");
        retVal = AT_CMD_RESEND;
        goto Exit_Handler;

    } else {
        LOGE(TAG"Error occured polling for response.  errno: %d\n", errno);
        retVal = AT_CMD_RESEND;
        goto Exit_Handler;
    }

    retVal = AT_CMD_OK;

Exit_Handler:
    return retVal;
}

static void fdclose()
{
if (md_fd != -1) {
close(md_fd);
md_fd = -1;
}
if (pc_fd != -1) {
/* Add errno trace in case that "unable write usb value" problem of BZ4161 is reproduced.*/
if (close(pc_fd) < 0) {
LOGE("close(pc_fd:%d) failed, error: %d, %s\n", pc_fd, errno, strerror(errno));
}
pc_fd = -1;
}
}