在C中制作自己的shell

Question

我正在尝试用C创建自己的shell,但是我遇到了strtok的问题.我使用它来正确地解析输入中的命令和参数,但我无法解析路径(它目前是段错误).一旦我正确解析了路径,我应该能够在每个部分上调用execlp并相应地进行fork处理.任何见解将不胜感激,代码如下.如果您认为我可以做得更好,也可以随意评论风格选择.

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

void parse(char *, char *);
void process(char *, char *, int);

int main(int argc, char *argv[]) {
  char *command;
  char *path;
  char buffer[1024];
  command = (char *)malloc(sizeof(char));
  path = (char *)malloc(sizeof(char));
  int loop = 1;
  while(loop == 1){
    path = getenv("MYPATH");
    if(path == NULL)
      path = "/bin#.";
    printf("($MYPATH is %s)\n", path);

    printf("myshell$ ");
    command = fgets(buffer, 1024, stdin);
    printf("Buffer: %s", buffer);
    printf("Command: %s", command);

    if(strcmp(command,"exit\n") == 0 || strcmp(command, "quit\n") == 0){
      loop = 0;
      printf("Program Terminated\n");
    }
    parse(command, path);
  }
  return 0;
}

void parse(char *command, char *path){
  char *argv;
  int argNum = 0;
  argv = strtok(command, " ");
  while(argv != NULL){
    printf("%s %d\n", argv, argNum);
    argv = strtok (NULL, " ");
    argNum++;
    }
  printf("Calling...\n");
  process(argv, path, argNum);
  printf("Called\n");
}

void process(char *argv, char *path, int argNum){
  char *pathPiece;
  int pathNum = 0;
  pathPiece = strtok(path, "#");
  while(pathPiece != NULL){
    printf("%s %d\n", pathPiece, pathNum);
    pathPiece = strtok(NULL, "#");
    pathNum++;
  }
}

Answer 1

您正在设置指向只读内存位置的路径,并且strtok在strtok尝试对其进行标记时(即在其中的某处写入空字符),调用它可能是您遇到问题的原因.

你可能需要这样的东西:

char path[1024];

并打电话给strcpy:

strcpy(path, getenv("MYPATH"));

和

strcpy(path, "/bin#.");

我强烈建议你阅读C中的字符串处理.