Question

所以我有一个shell代码：

#include <stdio.h>
#include <stdlib.h>
#define MAX_NUM_ARGS 256
#define SIZE 256

void orders(char *command[SIZE]);

int main() {

    char buffer[SIZE]= "";
    //char input_args[MAX_NUM_ARGS];
    char **input_args = NULL;
    int i = 0;// counting variable
    int blah = 0;

    printf("Welcome to the AY shell.\n");
  while(1){

    //initialize array of strings
    //first free any prevously allocated memory
    if (input_args != NULL)
    {   //memory has been allocated free it
        for (i = 0; i <MAX_NUM_ARGS; i++)
        {
            free(input_args[i]);
        }
    }   
    //free array of strings
    free(input_args);

    //new allocate memory
    input_args = (char**) malloc(sizeof(char*) * MAX_NUM_ARGS);
    //check return value for error
    if (input_args == NULL)
    {
        printf("We are out of memory. =(\n");
        continue;
        //print error: out of memory, exit with a error code
        exit(0);
    }
    //allocate memory for each string
    for (i = 0; i <MAX_NUM_ARGS; i++)
    { 
        input_args[i]= (char*)malloc(sizeof(char) * MAX_NUM_ARGS);
        if(input_args[i] == NULL)
            {//error
            printf("Error, the input is empty.");
            continue;
            }//end of if statement
    }//end of for loop


    printf("~$: "); //prompts the user for input
    fgets(buffer, sizeof(buffer), stdin);
    //if the user types in exit, quit
    if (strcmp(buffer, "exit\n") == 0){ 
        exit(0);
    } //end of if statement
    //if user types in clear, wipe the screen and repeat the lop
    else if(strcmp(buffer, "clear\n")==0){

        system("clear");    
        continue;   

    }//end of else if
    //should the user punch in nothing, repeat the loop
    else if (strcmp(buffer, "\n") == 0) {
        continue;
    }//end of else if


    input_args[1] = NULL;

    for (i = 0; i < SIZE; i++) {

        if(buffer[i] != '\n' && buffer[i] != ' ' && buffer[i] != '\t'){

            input_args[0][i] = buffer[i];
        }   //end of if statement
        else{
            input_args[0][i] = '\0';

        }//end of else statment

    }//end of for loop

    //if the input doesn't fall under the conditionals above, execute orders.
    orders(input_args);


   } //end of while loop
    return 0;

}//end of main function

void orders(char *command[SIZE]){
//handles the commands of the shell

    int retval = 0; //return value
    int pid = 0;
    int childValue = 0;
    pid = fork();

    if (pid != 0){
    //  printf("I'm the parent, waiting on the child.\n");//debug
        pid = waitpid(-1, &childValue,0);
    //  printf("Child %d returned a value of %x in hex.\n", pid, childValue);
        return;//return backs to the main prompt
    }//end of if statement
    else{
    //  printf("I am the first child.\n");
        retval = execvp(command[0], command);
        exit(2);
        if (retval != -1){
            //print error!
            printf("Invalid command!\n");
            exit(2);
        }
    }//end of else block


}//end of orders function

现在，它可以很好地执行clear，exit和单词命令，比如ls或pwd。但是，诸如“vim”之类的多行命令不起作用，也不会更改目录。

我做错了什么？

我怀疑retval = execvp（command [0]，command）;造成问题，但我不太确定。有什么想法吗？我不想直接回答，因为这是家庭作业，只是朝着正确的方向发展。

Answer 1

本节：

input_args[1] = NULL;

for (i = 0; i < SIZE; i++) {

    if(buffer[i] != '\n' && buffer[i] != ' ' && buffer[i] != '\t'){

        input_args[0][i] = buffer[i];
    }   //end of if statement
    else{
        input_args[0][i] = '\0';

    }//end of else statment

}//end of for loop

将input_args限制为仅使用第一个索引。我假设您可以找到在j++;子句中使用else并使用input_args[j][i]或类似内容的方法......

您的上一条评论与此匹配，因为您的retval = execvp(command[0], command);也只使用了列表中的第一项。

自定义shell只接受一个参数

1 个答案: