myshell.c

这是个在Linux系统下用C编写的一个shell程序

        }
    }
}

/*
 * open vi editor
 *
 * vi &
 */
void my_vi(options)
    char **options;
{
    pid_t pid;
    char *argv[11] = { NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL};
    int arg_index = 0;
    struct sigaction sa;

    if ((pid = fork()) < 0)
    {
        my_err_handler("fork error");
        return;
    }
    else if (pid == 0)
    {
        setpgid(pid, pid);
        argv[arg_index ++] = vi_path;

        if (*(options + 1) == NULL)
        {
            my_err_handler(unsupport_cmd);
            exit(0); 
        }
        else if (*(options + 1)[0] == '&')
        {
            if (execv(argv[0], argv) < 0)
            {
                my_err_handler("execv error");
                exit(0); 
            }
        }
        else
        {
            my_err_handler(unsupport_cmd);
            exit(0);
        }
    }
    else
    {
        setpgid(pid, pid);
        int tty = open("/dev/tty", O_RDWR);
        if (tty == -1)
        {
            my_err_handler("open error");
            return;
        }
        pid_t fg = getpgrp();
        if (tcsetpgrp(tty, fg) == -1)
        {
            my_err_handler("tcsetpgrp error");
            return;
        }
    }
}

/*
 * add serveral numbers read from stdin, no matter it is decimal or hexadecimal
 */
void my_add(numbers)
    char **numbers;
{
    long sum = 0;
    long value = 0;

    int i;
    for (i = 1; *(numbers + i) != NULL; i ++)
    {
        fprintf(stdout, "%s ", *(numbers + i));
        if (*(numbers + i + 1) != NULL)
            fprintf(stdout, "+ ");
        else
            fprintf(stdout, "= ");
        value =  get_number(*(numbers + i));
        if (value == -1)
        {
            sum = -1;
            return;
        }
        else
            sum += value;
    }
    fprintf(stdout, " %d\n", sum);
}

/*
 * translate string value to decimal
 */
long get_number(str_value)
    char *str_value;
{
    long value = 0;
    int length = strlen(str_value);

    if (str_value[0] == '0' && (str_value[1] == 'x' || str_value[1] == 'X'))
    {
       int i;
       for (i = 2; i < length; i ++)
       {
           if (isxdigit(str_value[i]))
           {
               switch(str_value[i])
               {
                   case '0':
                       value += 0 * (long)pow((double)16, (double)length - 1 - i);
                       break;
                   case '1':
                       value += 1 * (long)pow((double)16, (double)length - 1 - i);
                       break;
                   case '2':
                       value += 2 * (long)pow((double)16, (double)length - 1 - i);
                       break;
                   case '3':
                       value += 3 * (long)pow((double)16, (double)length - 1 - i);
                       break;
                   case '4':
                       value += 4 * (long)pow((double)16, (double)length - 1 - i);
                       break;
                   case '5':
                       value += 5 * (long)pow((double)16, (double)length - 1 - i);
                       break;
                   case '6':
                       value += 6 * (long)pow((double)16, (double)length - 1 - i);
                       break;
                   case '7':
                       value += 7 * (long)pow((double)16, (double)length - 1 - i);
                       break;
                   case '8':
                       value += 8 * (long)pow((double)16, (double)length - 1 - i);
                       break;
                   case '9':
                       value += 9 * (long)pow((double)16, (double)length - 1 - i);
                       break;
                   case 'a':
                   case 'A':
                       value += 10 * (long)pow((double)16, (double)length - 1 - i);
                       break;
                   case 'b':
                   case 'B':
                       value += 11 * (long)pow((double)16, (double)length - 1 - i);
                       break;
                   case 'c':
                   case 'C':
                       value += 12 * (long)pow((double)16, (double)length - 1 - i);
                       break;
                   case 'd':
                   case 'D':
                       value += 13 * (long)pow((double)16, (double)length - 1 - i);
                       break;
                   case 'e':
                   case 'E':
                       value += 14 * (long)pow((double)16, (double)length - 1 - i);
                       break;
                   case 'f':
                   case 'F':
                       value += 15 * (long)pow((double)16, (double)length - 1 - i);
                       break;
                   default:
                       break;
               }
               return value;
           }
           else
           {
               fprintf(stdout, "%s\t", str_value[i]);
               my_err_handler("Wrong format of hexadecimal number!");
               return -1;
           }
       }
   }
   else
   {
       int i;
       for (i = 0; i < length; i ++)
       {
           if (isdigit(str_value[i]))
           {
               switch(str_value[i])
               {
                   case '0':
                       value += 0 * (long)pow((double)10, (double)length - 1 - i);
                       break;
                   case '1':
                       value += 1 * (long)pow((double)10, (double)length - 1 - i);
                       break;
                   case '2':
                       value += 2 * (long)pow((double)10, (double)length - 1 - i);
                       break;
                   case '3':
                       value += 3 * (long)pow((double)10, (double)length - 1 - i);
                       break;
                   case '4':
                       value += 4 * (long)pow((double)10, (double)length - 1 - i);
                       break;
                   case '5':
                       value += 5 * (long)pow((double)10, (double)length - 1 - i);
                       break;
                   case '6':
                       value += 6 * (long)pow((double)10, (double)length - 1 - i);
                       break;
                   case '7':
                       value += 7 * (long)pow((double)10, (double)length - 1 - i);
                       break;
                   case '8':
                       value += 8 * (long)pow((double)10, (double)length - 1 - i);
                       break;
                   case '9':
                       value += 9 * (long)pow((double)10, (double)length - 1 - i);
                       break;
                   default:
                       break;
               }
               return value;
           }
           else
           {
               //fprintf(stdout, "%s\t", str_value[i]);
               my_err_handler("Wrong format of decimal number!");
               return -1;
           }
       }
   }
}

/*
 * count arguments and list them
 */
void my_args(args)
    char **args;
{
    int argc = 0;
    int i = 0;
   
    fprintf(stdout, "args = ");
    if (args[1] != NULL)
    {
        fprintf(stdout, "%s", args[1]);
        i ++;
    }

    for (; *(args + i + 1) != NULL; i ++)
        fprintf(stdout, ", %s", args[i + 1]);
    argc = i;
    fprintf(stdout, "\targc = %d\n", argc);
}

/*
 * display history commands
 */
void my_history(options)
    char **options;
{
    if (*(options + 1) != NULL)
    {
        my_err_handler(unsupport_cmd);
        return;
    }

    int index = history_cmd_index;
    int i, j;
    if (strlen(history_cmds[index][0]) == 0)
    {
        int temp = index;
        while (strlen(history_cmds[temp][0]) == 0)
            temp  = ++temp % 10;
        for (i = 0; temp != index; temp = ++temp % 10, i ++)
        {
            fprintf(stdout, "%d\t", i);
            for (j = 0; strlen(history_cmds[temp][j]) != 0; j ++)
                fprintf(stdout, "%s ", history_cmds[temp][j]);
            fprintf(stdout, "\n");
        }
    }
    else
    {
        for (i = 0; i < 10; i ++)
        {
            fprintf(stdout, "%d\t", i);
            for (j = 0; strlen(history_cmds[index][j]) != 0; j ++)
                fprintf(stdout, "%s ", history_cmds[index][j]);
            fprintf(stdout, "\n");
            index = ++ index % 10;
        }
    }
}

/*
 * execute one history method use "! cmd_no"
 */
void my_ex_hcmd(number)
    char **number;
{
    if ((number + 1) == NULL)
    {
        my_err_handler("Please enter a history commond number!");
        return;
    }

    int index = (int)get_number(*(number + 1));
    if (index > 9)
    {
        my_err_handler("Wrong history commond number!");
        return;
    }

    int j;
    fprintf(stdout, "%d\t", index);
    for (j = 0; strlen(history_cmds[index][j]) != 0; j ++)
        fprintf(stdout, "%s ", history_cmds[index][j]);
    fprintf(stdout, "\n");
}

/*
 * add current cmd to history array
 */
void add_history_cmd(cmd)
    char **cmd;
{
    int i;
    for (i = 0; *(cmd + i) != NULL; i ++)
    {
        memcpy(history_cmds[history_cmd_index][i], cmd[i], 10);
    }
    history_cmd_index = ++ history_cmd_index % 10;
}

/*
 * Error handler, display the error information to user.
 */
void my_err_handler(err_str)
    const char *err_str;
{
    fprintf(stderr, "%s\n", err_str);
}