c - 段错误 - strcpy() - C

Question

我正在为命令行 shell 实现历史记录功能。我已经实现了一个循环数组来保存十个最近的命令。每个命令还用一个整数来标记，指定总命令是什么。例如，如果总共输入 30 个命令，则循环数组中的 10 个命令将编号为 (30, 29, 28, 27,...,21)。

如果用户要插入命令“r”，后跟一个标记十条指令之一的数字，则该指令应该运行。当我试图确保正确接受两个字的命令时，我不断遇到段错误。谁能帮忙指出问题所在。

int main(void)
{
    char inputBuffer[MAX_LINE]; /* buffer to hold the command entered */
    int background;             /* equals 1 if a command is followed by '&' */
    char *args[MAX_LINE/2+1];/* command line (of 80) has max of 40 arguments */

    int position, count, rnum = 0;
    char historyArray[10][MAX_LINE];
    char *holder[MAX_LINE]={0};

    while (1){            /* Program terminates normally inside setup */
        background = 0;
        printf("COMMAND->");
        fflush(0);

        setup(inputBuffer, args, &background);       /* get next command */

        position = (count % MOD_VAL);
        strcpy(historyArray[position],args[0]);

        if(!strcmp("rr",args[0]))
        {
            strcpy(historyArray[position],historyArray[((position-1)+MOD_VAL)%MOD_VAL]);
            printf("%i",count);
            printf("%c",'.');
            printf("%c",' ');
            printf("%s",historyArray[position]);
            printf("%c",'\n');
            strcpy(args[0],historyArray[position]);
        }

        else if(!strcmp("r",args[0])) //SEG FAULT OCCURING IN THIS ELSE-IF BLOCK!
        {
            //args[1] will hold given number
            printf("%c",'\n');
            printf("%s",args[0]);
            printf("%s",args[1]);
            printf("%s",args[2]);
            printf("%c",'\n'); //PRINT STATEMENTS FOR DEBUGGING

            strncpy(holder[0], args[2], MAX_LINE - 1); //SEG FAULT

            rnum = atoi(args[1]);
            strcpy(historyArray[position],historyArray[((position-(count-rnum))+MOD_VAL)%MOD_VAL]);
            strcpy(args[0],historyArray[position]); //CHANGES VALUES OF args[1], args[2]

            if(holder[0] != NULL)
            {
                strncpy(args[1],holder[0],MAX_LINE-1);
                args[2] = NULL;
            }
            else
            {
                args[1] = NULL;
            }

            printf("%c",'\n');
            printf("%s",args[0]);
            printf("%s",args[1]);
            printf("%s",args[2]);
            printf("%c",'\n');
        }

        else if(!(strcmp("h",args[0]))||!(strcmp("history",args[0])))
        {
            int counter = 0;
            while(counter < 10)
            {
                printf("%i",(count - counter));
                printf("%c",'.');
                printf("%c",' ');
                printf("%s", historyArray[((position - counter + MOD_VAL)%MOD_VAL)]);
                printf("%c",' ');
                printf("%c",'\n');
                counter ++;

                if(counter > count)
                    break;
            }
        }
        count++;

        pid_t pid1; //Initialize pid_t variable to hold process identifier
        pid1 = fork(); //Fork process and assign process identifier to "pid1"

        if (pid1 == 0) //Child process
        {
            //Child process executes the command specified by the user and
            //then quits.
            execvp(args[0], args);
            exit(0);
        }
        else //Parent process
        {
            if (background != 1)//Check for inclusion of '&' in command 
            {
                wait(NULL); //Wait for child process to finish executing
            }
        } 

        /* the steps are:
         (1) fork a child process using fork()
         (2) the child process will invoke execvp()
         (3) if background == 0, the parent will wait, 
         otherwise returns to the setup() function. */
    }
}

感谢任何帮助!

-哑光

Answer 1

这里的 args 是字符指针数组。

但是strcpy需要两个参数 - 这应该是数组或由malloc分配的内存的字符指针

但是您的 strcpy(historyArray[position],args[0]); 将一个参数作为字符指针，这将不会被接受。

因此您可以将 args[] 更改为 args[][] 或 args[0] = malloc(some_no)， segfault 将被删除。