如何扩展我的功能以获得cd命令？

I'm writing a small shell in C as an exercis to learn about linux and C. Now I can execute custom commands and the exit command, but I can't execute a builtin CD command since I don't know how to split it in two part (the cd command and the name of the directory to CD to).

我正在用C语言编写一个小shell来学习linux和C.现在我可以执行自定义命令和exit命令，但我不能执行内置CD命令，因为我不知道如何拆分它分两部分（cd命令和CD到目录的名称）。

The desired functionality is that my program should accept the cd command with a parameter that is the directory. I can do it with command-line arguments but I don't know how to do it in its current form. How can it be done?

所需的功能是我的程序应该接受带有作为目录的参数的cd命令。我可以用命令行参数来做，但我不知道如何以当前的形式做到这一点。如何做呢？

#include <sys/stat.h>
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <dirent.h>
#include <errno.h>
#include <stdarg.h>
#include <stdlib.h>
#include <signal.h>
#include <sys/types.h>
#include <sys/wait.h>

#define BUFFER_LEN 1024
#define BUFFERSIZE 1024


int mystrcmp(char const *, char const *);


void err_syserr(char *fmt, ...)
{
    int errnum = errno;
    va_list args;
    va_start(args, fmt);
    vfprintf(stderr, fmt, args);
    va_end(args);
    if (errnum != 0)
        fprintf(stderr, "(%d: %s)\n", errnum, strerror(errnum));
    exit(EXIT_FAILURE);
}
int main() {
    char line[BUFFER_LEN];  
    char* argv[100];        
    char* path= "/bin/";    
    char progpath[20];      
    int argc;               
    size_t length;
    char *token;
    int i=0;
    int pid;
    while(1) {
    i = 0;
        printf("miniShell>> ");                    

        if(!fgets(line, BUFFER_LEN, stdin)) { 
            break;                                
        }
        length = strlen(line);
        if (line[length - 1] == '\n') {
            line[length - 1] = '\0';
        }
        if(strcmp(line, "exit")==0) {           
            break;
        }
    if(strcmp(line, "cd")==0) {           
            /*printf("change directory to %s\n", argv[2]);
            chdir(argv[2]);*/
        }

        token = strtok(line," ");

        while(token!=NULL) {
            argv[i]=token;
            token = strtok(NULL," ");
            i++;
        }
        argv[i]=NULL;                     

        argc=i;                           
        for(i=0; i<argc; i++) {
            printf("%s\n", argv[i]);      
        }
        strcpy(progpath, path);           
        strcat(progpath, argv[0]);            

        for(i=0; i<strlen(progpath); i++) {   
            if(progpath[i]=='\n') {
                progpath[i]='\0';
            }
        }
        pid= fork();              

        if(pid==0) {              
            execvp(progpath,argv);
            fprintf(stderr, "Child process could not do execvp\n");

        } else {                  
            wait(NULL);
            printf("Child exited\n");
        }

    }
return (0);
}

int mystrcmp(char const *p, char const *q)
{
    int i = 0;
    for(i = 0; q[i]; i++)
    {
        if(p[i] != q[i])
            return -1;
    }
    return 0;
}

int cd(char *pth) {
    char path[BUFFERSIZE];
    char cwd[BUFFERSIZE];
    char * return_value;
    int other_return;
    strcpy(path,pth);

    if(pth[0] != '/')
    {  
        return_value = getcwd(cwd,sizeof(cwd));
        strcat(cwd,"/");
        strcat(cwd,path);
        other_return = chdir(cwd);
    } else { 
        other_return = chdir(pth);
    }
    printf("Spawned foreground process: %d\n", getpid());
    return 0;
}

2 个解决方案

#1

Use strpbrk or strsep to split your input into white-space separated tokens, then use strcmp on the first one and use the remaining ones as arguments.

使用strpbrk或strsep将输入拆分为空格分隔的标记，然后在第一个使用strcmp并使用其余的作为参数。

This answer to a related question has an example, and here are some notes on portability.

这个相关问题的答案有一个例子，这里有一些关于可移植性的注释。

#2

I'd suggest to parse your argument with the getopt function from unistd library. It's covered in this question too.

我建议用unistd库中的getopt函数解析你的参数。它也包含在这个问题中。

Here is the documentation for getopt command.

这是getopt命令的文档。

#1