fork process always return > 0 我不明白为什么?

fork process always returning > 0 i cannot figure out why?

你好,我正在用 C 创建一个简单的 shell,目前我遇到了 fork 的问题,因为它似乎总是 return 值 > 0,即使我输入一些非 linux 命令,如“ehshhduh”,它仍然会打印出“智利进程完成”,而不是 return 发出错误消息,谁能向我解释我做错了什么,谢谢?

#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h> 
#include <string.h>
#include <unistd.h>
#include <sys/types.h>


char str_tokens[50];

char * get_input() {
    pid_t pid; 
    char *tokens[30][50];
    char input[512];
    char *charp;
    char *burner[20];
  
    int i = 0;

while(true) {
   printf(">");
   if(fgets(input, 512, stdin) == 0 || strncmp(input, "exit", 4) == 0) {    /* reads in input from user no more than 512 chars including null terminator, program terminates if "exit" or CTRL-D is detected*/
     printf("exitting program");
       exit(0);
   } 

    const char delimiters[9] = {'&', ';', '\n', '|', ' ', '\t', '>', '<',}; 
    charp = strtok(input, delimiters); /* splits the string on delimiters */
    while (charp != NULL) {
      
         strcpy(str_tokens, charp);
        charp = strtok(NULL, delimiters);   // sets the char pointer to null
                                                //after each split of the string 
                                                //so the loop eventually terminates */
        } 
       char *args[] = {str_tokens, 0};  

    pid = fork();     // fork a child process
    if (pid == -1) { /* error occured */
        fprintf(stderr, "Error occured with Fork");
        return 1;
    }
     else if (pid > 0) {  /* parent process */
        /* parent will wait for the child process to complete */
        wait(NULL);
        printf("Child process completed") ;
    }
    else if(pid == 0){ // (pid == 0)  /* this is the child process */
        execvp(args[0], args);          /* first param the file path, seconf is null terminated array of char pointers*/
        printf("this is the child process");
        _exit(EXIT_FAILURE);            /* in the case our exec never returns exit */
    }
   

    }
  
   return str_tokens;
}


void run_external(char* commands[50]) {
    commands = get_input();
}

int main () {
 run_external(get_input());
   return(0);
    
}

fork 的调用发生在 在您对新程序调用 execvp 之前

首先您创建一个新进程,然后当您成功完成后,您尝试在该进程中启动一个新程序。如果程序名称无效,则 execvp returns 而您 _exit 子进程。

此外,当 forkexecvp 失败时,您应该调用 perror。这将打印一条描述原因的错误消息。