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我尝试做一些关于在 linux 中使用 execv 创建进程的家庭作业。我需要从用户那里获取一个输入字符串，并检查机器上是否有同名的程序。我需要尝试使用 PATH 变量目录执行给定的程序字符串，我必须仅使用 execv 函数来执行程序。当第一个单词是程序的文件，其他单词是参数时，输入以空格分隔。他们还要求我验证环境是否已传递给 execv。我该如何检查？我发现我需要使用environ变量并填充它

到目前为止，我已经尝试过：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define MYCOMMAND_LEN   1000
#define MYNUM_OF_PARAMS 500

extern char **environ;

int main()
{
    int i = 0, j, pid, stat, amountOfLib;
    char command[MYCOMMAND_LEN];
    char *params[MYNUM_OF_PARAMS];
    char *path, *lastStr;
    char *libs[100];
    int numberOflib = 0, numOfParams;
    char *commandPath;

    //cut path
    path = getenv("PATH");
    lastStr = strtok(path, ":");
    libs[0] = (char*)malloc(sizeof(char)*strlen(lastStr) + 1);
    strcpy(libs[0], lastStr);
    i = 1;
    while (lastStr = strtok(NULL, ":")) {
        libs[i] = (char*)malloc(sizeof(char)*strlen(lastStr) + 1);
        strcpy(libs[i], lastStr);
        i++;
        numberOflib = i;
    }
    numberOflib = i;


    puts("Please Enter Command: ");
    gets(commandPath);

    //loop until leave {
    while (strcmp(command, "leave") != 0) {

        //cut command
        lastStr = strtok(command, " ");
        params[0] = (char*)malloc(sizeof(char)*(strlen(lastStr) + 1));
        strcpy(params[0], lastStr);
        i = 1;
        while ((lastStr = strtok(NULL, " ")) != NULL)
        {
            params[i] = (char*)malloc(sizeof(char)*(strlen(lastStr) + 1));
            strcpy(params[i], lastStr);
            i++;
        }
        params[i] = NULL;
        numOfParams = i;

        //check if first is relative
        if ((pid = fork()) == 0) {
            if (params[0][0] == '/' ||
                (strlen(params[0]) >= 2 &&
                    params[0][0] == '.' &&
                    params[0][1] == '/'
                    ) ||
                    (strlen(params[0]) >= 3 &&
                        params[0][0] == '.' &&
                        params[0][1] == '.' &&
                        params[0][2] == '/'
                        )
                ) execv(params[0], params);
            // if command like "man ls"
            else {
                for (i = 0; i < amountOfLib; i++) {
                    commandPath = libs[i];
                    strcat(commandPath, "/");
                    strcat(commandPath, params[0]);

                    for (j = 0; j < numOfParams; j++) {
                         environ[j] = params[j]; //last environ also get the null
                    }

                    execv(commandPath, NULL);
                }
                puts("command not found in PATH");
                exit(1);
            }
        } else {
            wait(&stat);
        }
        puts("Please Enter Command: ");
        gets(commandPath);
    }
    //}

}

像“ls”这样的一些输入回复 argv 向量为空。

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