main.c

#include <stdio.h>
#include <sys/wait.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>

/* 
Function declarations for builtin shell commands
*/
int lsh_cd(char **args);
int lsh_help(char **args);
int lsh_exit(char **args);

/* 
List of builtin commands followed by thier corresponding functions
*/
char *builtin_str[] = {
    "cd",
    "help",
    "exit"
};

int (*builtin_func[])(char **) = {
    &lsh_cd,
    &lsh_help,
    &lsh_exit
};

int lsh_num_builtins() {
    return sizeof(builtin_str) / sizeof(char *);
}

/* 
Builtin function implemetations
*/
int lsh_cd(char **args) {
    if (args[1] == NULL) {
        fprintf(stderr, "lsh: expected argument to \"cd\"\n");
    } else {
        if (chdir(args[1]) != 0) {
            perror("lsh");
        }
    }

    return 1;
}

int lsh_help(char **args) {
	(void)args;
    int i;
    printf("750yen SHELL\n");
    printf("Type program names and arguments, and hit enter.\n");
    printf("The following are built in: \n");

    for (i = 0; i < lsh_num_builtins(); i++) {
        printf(" %s\n", builtin_str[i]);
    }

    printf("Use the man command for information on other programs.\n");

    return 1;
}

int lsh_exit(char **args) {
	
    return 0;
}

int lsh_execute(char **args) {
    int i;

    if (args[0] == NULL) {
        return 1;
    }

    for (i = 0; i < lsh_num_builtins(); i++) {
        if (strcmp(args[0], builtin_str[i]) == 0) {
            return (*builtin_func[i])(args);
        }
    }

    return lsh_launch(args);
}


int lsh_launch(char **args) {
    pid_t pid, wpid;
    int status;

    pid = fork();
    if (pid == 0) {
        // 子プロセス
        if (execvp(args[0], args) == -1) {
            perror("lsh");
        }
        exit(EXIT_FAILURE);
    } else if (pid < 0) {
        // フォークでエラー
        perror("lsh");
    } else {
        // 親プロセス
        do {
            wpid = waitpid(pid, &status, WUNTRACED);
        } while (!WIFEXITED(status) && !WIFSIGNALED(status));
    }

    return 1;
}

#define LSH_TOK_BUFSIZE 64
#define LSH_TOK_DELIM " \t\r\n\a"
char **lsh_split_line(char *line) {
    int bufsize = LSH_TOK_BUFSIZE, position = 0;
    char **tokens = malloc(bufsize * sizeof(char*));
    char *token;

    if (!tokens) {
        fprintf(stderr, "lsh:allocation error\n");
        exit(EXIT_FAILURE);
    }

    token = strtok(line, LSH_TOK_DELIM);
    while (token != NULL) {
        tokens[position] = token;
        position++;
        
        if (position >= bufsize) {
            bufsize += LSH_TOK_BUFSIZE;
            tokens = realloc(tokens, bufsize * sizeof(char*));
            if (!tokens) {
                fprintf(stderr, "lsh: allocation error\n");
                exit(EXIT_FAILURE);
            }
        }
        token = strtok(NULL, LSH_TOK_DELIM);
    }
    tokens[position] = NULL;
    return tokens;
}

#define LSH_RL_BUFSIZE 1024
// char *lsh_read_line(void) {
//     int bufsize = LSH_RL_BUFSIZE;
//     int position = 0;
//     char *buffer = malloc(sizeof(char) * bufsize);
//     int c;

//     if (!buffer) {
//         fprintf(stderr, "lsh: allocation error\n");
//         exit(EXIT_FAILURE);
//     }

//     while (1) {
//         c = getchar();

//         // 終了まできたらnullにして終わり
//         if (c == EOF || c == '\n') {
//             buffer[position] = '\0';
//             return buffer;
//         } else {
//             buffer[position] = c;
//         }
//         position++;

//         // もしbufferを超えた時
//         if (position >= bufsize) {
//             bufsize += LSH_RL_BUFSIZE;
//             buffer = realloc(buffer, bufsize);
//             if (!buffer) {
//                 fprintf(stderr, "lsh: allocation error\n");
//                 exit(EXIT_FAILURE);
//             }
//         }
//     }
// }

char *lsh_read_line(void) {
    char *line = NULL;
    ssize_t bufsize = 0;
    getline(&line, &bufsize, stdin);
    return line;
}


void lsh_loop(void) {
    char *line;
    char **args;
    int status;

    do {
        printf("> ");
        line = lsh_read_line();
        args = lsh_split_line(line);
        status = lsh_execute(args);

        free(line);
        free(args);
    } while (status);
}

int main(int argc, char *argv[]) {
  // Load config files, if any.

  (void)argc;
  (void)argv;

  // Run command loop.
  lsh_loop();

  // Perform any shutdown/cleanup.

  return EXIT_SUCCESS;
}