linux系统errno 22

#include <stdio.h>
#include <fcntl.h>
#include <errno.h>

int main() {
    int fd = open("nonexistent_file", O_RDWR); // 文件不存在且尝试读写
    if (fd == -1) {
        perror("open");
        printf("Error code: %d\n", errno);
    }
    return 0;
}

#include <sys/socket.h>
#include <netinet/in.h>
#include <stdio.h>
#include <errno.h>

int main() {
    int sockfd = socket(AF_INET, SOCK_STREAM, 0);
    if (sockfd < 0) {
        perror("socket");
        return 1;
    }

    int optval = 1;
    if (setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &optval, sizeof(optval)) < 0) {
        perror("setsockopt");
        printf("Error code: %d\n", errno);
    }
    return 0;
}

#include <sys/mman.h>
#include <stdio.h>
#include <errno.h>

int main() {
    void *addr = mmap(NULL, 1024, PROT_READ | PROT_WRITE, MAP_SHARED, -1, 0);
    if (addr == MAP_FAILED) {
        perror("mmap");
        printf("Error code: %d\n", errno);
    }
    return 0;
}