检查 C 中 argc 的值

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Checking value of argc

我将继续进行套接字编程，这是我在 linux-ubuntu 上开发的套接字编程简单 C 代码，但由于代表端口的 argc 值，代码无法工作并在第一个 if 条件下退出。 我需要帮助:)

#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>
#include <string.h>
#include <stdio.h>
const char APRESSMESSAGE[] = "APRESS - For Professionals, By Professionals!\n";

int main(int argc, char *argv[]) {
int simpleSocket = 0;
int simplePort = 0;
int returnStatus = 0;
struct sockaddr_in simpleServer;

if (2 != argc) {
    fprintf(stderr, "Usage: %s <port>\n", argv[0]);
    exit(1);
}
simpleSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
printf("%i\n", simpleSocket);
if (simpleSocket <= -1) {
    fprintf(stderr, "Could not create a socket!\n");
    exit(1);
} else {
    fprintf(stderr, "Socket created!\n");
}
/* retrieve the port number for listening */
simplePort = atoi(argv[1]);
/* set up the address structure */
/* use INADDR_ANY to bind to all local addresses
 */
puts("test1");
bzero(&simpleServer, sizeof(simpleServer));
simpleServer.sin_family = AF_INET;
simpleServer.sin_addr.s_addr = htonl(INADDR_ANY);
simpleServer.sin_port = htons(simplePort);
/*
 bind to the address and port with our socket
 */
returnStatus = bind(simpleSocket, (struct sockaddr *) &simpleServer,
        sizeof(simpleServer));
if (returnStatus == 0) {
    fprintf(stderr, "Bind completed!\n");
} else {
    fprintf(stderr, "Could not bind to address!\n");
    close(simpleSocket);
    exit(1);
}
/* let's listen on the socket for connections */
returnStatus = listen(simpleSocket, 5);
if (returnStatus == -1) {
    fprintf(stderr, "Cannot listen on socket!\n");
    close(simpleSocket);
    exit(1);
}
while (1) {
    struct sockaddr_in clientName = { 0 };
    int simpleChildSocket = 0;
    int clientNameLength = sizeof(clientName);
    /* wait here */
    simpleChildSocket = accept(simpleSocket,
            (struct sockaddr *) &clientName, &clientNameLength);
    if (simpleChildSocket == -1) {
        fprintf(stderr, "Cannot accept connections!\n");
        close(simpleSocket);
        exit(1);
    }
    /* handle the new connection request
     */
    /* write out our message to the client */
    write(simpleChildSocket, APRESSMESSAGE, strlen(APRESSMESSAGE));
    close(simpleChildSocket);
}
close(simpleSocket);
return 0;

}

Answer 1

我不太确定您在问什么，但我相信您对检查传递给程序的参数数量的 if 语句如何工作感到困惑。从命令行，如果用户运行:

myprogram

argv 的值将为 {"myprogram"} 且 argc 将为 1。另一方面，如果您运行:

myprogram 23

argv 的值将是 {"myprogram", "23"} 和 argc 将是 2。我认为你只是运行程序时未传递适当的端口号参数。