myshell.c

这是个在Linux系统下用C编写的一个shell程序

#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <string.h>
#include <math.h>
#include <ctype.h>
#include <errno.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <signal.h>

#include "myshell.h"

#define RWXRXRX (S_IRUSR | S_IWUSR | S_IXUSR | S_IRGRP | S_IXGRP | S_IROTH | S_IXOTH)
/*
 * functions not defined in this file
 */
extern char **getline();

/*
 * initialization goes here
 */

char incorrect_cmd[128] = "Sorry, you just entered incorrect command!";
char unsupport_cmd[128] = "Sorry, myshell doesn't support this use!";

char *ls_path = "/usr/bin/ls";
char *sort_path = "/usr/bin/sort";
char *more_path = "/bin/more";
char *less_path = "/usr/bin/less";
char *vi_path = "/usr/bin/vi";

char cmds_array[10][10][10];
char (*history_cmds)[10][10] = cmds_array; 
int history_cmd_index = 0;

char **args;

int main(int argc, char *argv[]) {

  /*
   * mask signals
   */
    struct sigaction sa;
    sa.sa_handler = SIG_IGN;
    sigemptyset(&sa.sa_mask);
    sa.sa_flags = 0;
    if (sigaction(SIGINT, &sa, NULL) < 0)
    {
        my_err_handler("sigint error");
        return;
    }
    if (sigaction(SIGQUIT, &sa, NULL) < 0)
    {
        my_err_handler("sighquit error");
        return;
    }
    if (sigaction(SIGTSTP, &sa, NULL) < 0)
    {
        my_err_handler("sigtstp error");
        return;
    }

  /*
   * The main loop always run, only Ctrl+\ can quit it.
   */
  while(1) 
  {
      fprintf(stdout, "myshell$ ");
      args = getline();
      add_history_cmd(args);
      /*
       * parse the commands
       */
      if (args[0] == NULL)
      {
          //'\n' only, do nothing 
      }
      else
      {
          if (strncmp(args[0], "exit", 4) == 0)
          {
              my_exit();
          }
          else if (strncmp(args[0], "ls", 2) == 0)
          {
              my_ls(args);
          }
          else if(strncmp(args[0], "sort", 4) == 0)
          {
              my_sort(args);
          }
          else if(strncmp(args[0], "vi", 2) == 0)
          {
              my_vi(args);
          }
          else if(strncmp(args[0], "add", 3) == 0)
          {
              my_add(args);
          }
          else if(strncmp(args[0], "args", 4) == 0)
          {
              my_args(args);
          }
          else if(strncmp(args[0], "history", 7) == 0)
          {
              my_history(args);
          }
          else if(strncmp(args[0], "!", 1) == 0)
          {
              my_ex_hcmd(args);
          }
          else
          {
              my_err_handler(unsupport_cmd);
          }
      }
  }

  return 0;
}

/*
 * use to exit myshell
 *
 * exit
 */
int my_exit()
{
    int status;
    exit(status);
    return status;
}

/*
 * use to list the current directory
 * with or without options
 * redirect output also implements here
 *
 * ls
 * ls -l
 * ls -l > foo
 * ls -l | more
 */
void my_ls(options)
    char **options;
{
    /* ls */
    pid_t pid;
    char *argv[11] = { NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL};
    int arg_index = 0;

    if ((pid = fork()) < 0)
    {
        my_err_handler("fork error");
        return;
    }
    else if (pid == 0)
    {
        argv[arg_index ++] = ls_path;
        if (*(options + 1) != NULL)
        {
            if (strncmp(*(options + 1), "-l", 2) == 0)
                argv[arg_index ++] = "-l";
            else
            {
                my_err_handler(unsupport_cmd);
                return;
            }

            if (*(options + 2) == NULL)
            {
                //do nothing
            }
            else if (*(options + 2)[0] == '>')
            {
                /* ls -l > foo */
                if (*(options + 3) == NULL)
                {
                    my_err_handler("no redirected output given!");
                    return;
                }
                else
                {
                    FILE *fp;
                    if ((fp = freopen(*(options + 3), "w", stdout)) == NULL)
                    {
                        my_err_handler("freopen error");
                        return;
                    }
                }
            }
            else if (*(options + 2)[0] == '|')
            {
                /* ls -l | more */
                pid_t pid2;
                int fd[2];
                if (pipe(fd) == -1)
                {
                    my_err_handler("pipe error");
                    return;
                }

                char *argv2[11] = { NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL};
                int arg_index2 = 0;
                if (strncmp(*(options + 3), "more", 4) == 0)
                {
                    argv2[arg_index2 ++] = more_path;
                }
                else if (strncmp(*(options + 3), "less", 4) == 0)
                {
                    argv2[arg_index2 ++] = less_path;
                }
                else
                {
                    my_err_handler(unsupport_cmd);
                    return;
                }
                if ((pid2 = fork()) < 0)
                {
                    my_err_handler("fork error");
                    return;
                }
                else if (pid2 == 0)
                {
                    close(fd[0]);
                    if (dup2(fd[1], STDOUT_FILENO) != STDOUT_FILENO)
                    {
                        my_err_handler("dup2 error");
                        return;
                    }
                    close(fd[1]);
                    if (execv(argv[0], argv) < 0)
                    {
                        my_err_handler("execv error");
                        return;
                    }
                }
                else
                {
                    close(fd[1]);
                    if (wait(NULL) < 0)
                    {
                        my_err_handler("wait error");
                        return;
                    }
                    if (dup2(fd[0], STDIN_FILENO) != STDIN_FILENO)
                    {
                        my_err_handler("dup2 error");
                        return;
                    }
                    close(fd[0]);
                    if (execv(argv2[0], argv2) < 0)
                    {
                        my_err_handler("execv error");
                        return;
                    }
                }
                return; //direct return, not execute code below
            }
            else
            {
                my_err_handler(unsupport_cmd);
                return;
            }
        }

        if (execv(argv[0], argv) < 0)
        {
            my_err_handler("execv error");
            return;
        }
    }
    else
    {
        if (wait(NULL) != pid)
        {
            my_err_handler("wait error");
            return;
        }
    }
}

/*
 * use to sort lines of a file
 * with redirect input
 *
 * sort < foo
 */
void my_sort(options)
    char **options;
{
    pid_t pid;
    char *argv[11] = { NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL};
    int arg_index = 0;

    if ((pid = fork()) < 0)
    {
        my_err_handler("fork error");
        return;
    }
    else if (pid == 0)
    {
        argv[arg_index ++] = sort_path;
        if (*(options + 1) == NULL)
        {
            //do nothing, will read from stdin
        }
        else if (*(options + 1)[0] == '<')
        { 
            if (*(options + 2) == NULL)
            {
                my_err_handler("no redirected input given!");
                return;
            }
            else
            {
                FILE *fp;
                if ((fp = freopen(*(options + 2), "r", stdin)) == NULL)
                {
                    my_err_handler("freopen error");
                    return;
                }
            }
        }
        else
        {
            my_err_handler(unsupport_cmd);
            return;
        }

        if (execv(argv[0], argv) < 0)
        {
            my_err_handler("execv error");
            return;
        }
    }
    else
    {
        if (wait(NULL) != pid)
        {
            my_err_handler("wait error");
            return;