Luna/apps/sh.cpp

#include <luna/String.h>
#include <luna/Vector.h>
#include <os/ArgumentParser.h>
#include <os/File.h>
#include <os/FileSystem.h>

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

using os::File;

static Result<Vector<char*>> split_command_into_argv(StringView cmd, char** out)
{
    char* str = strdup(cmd.chars());

    Vector<char*> result;

    char* segment = strtok(str, " \n");
    TRY(result.try_append(segment));

    if (segment == NULL) return result;

    for (;;)
    {
        segment = strtok(NULL, " \n");
        TRY(result.try_append(segment));

        if (segment == NULL) return result;
    }

    if (out) *out = str;

    return result;
}

[[noreturn]] static void execute_command(StringView command)
{
    Vector<char*> argv;
    bool ok = split_command_into_argv(command, nullptr).try_move_value_or_error(argv, errno);
    if (!ok)
    {
        perror("failed to parse command");
        exit(1);
    }

    if (argv[0] == NULL) exit(0);
    execvp(argv[0], argv.data());
    perror(argv[0]);
    exit(1);
}

Result<int> luna_main(int argc, char** argv)
{
    StringView path;
    StringView command;
    bool interactive { false };

    SharedPtr<File> input_file;

    os::ArgumentParser parser;
    parser.add_positional_argument(path, "path"_sv, "-"_sv);
    parser.add_value_argument(command, 'c', "command"_sv, true);
    parser.parse(argc, argv);

    if (!command.is_empty()) execute_command(command);

    if (path == "-")
    {
        input_file = File::standard_input();
        interactive = true;
    }
    else
    {
        input_file = TRY(File::open(path, File::ReadOnly));
        input_file->set_close_on_exec();
    }

    while (1)
    {
        if (interactive)
        {
            auto cwd = TRY(os::FileSystem::working_directory());
            printf("sh %s%c ", cwd.chars(), getuid() == 0 ? '#' : '$');
        }

        auto cmd = TRY(input_file->read_line());
        if (cmd.is_empty()) break;

        if (strspn(cmd.chars(), " \n") == cmd.length()) continue;

        if (!strncmp(cmd.chars(), "cd", 2))
        {
            char* copy = nullptr;

            auto args = TRY(split_command_into_argv(cmd.view(), &copy));
            check("cd"_sv == args[0]);

            if (args.size() == 2)
            {
                auto home = TRY(os::FileSystem::home_directory());
                if (chdir(home.chars()) < 0) perror("cd");
                free(copy);
                continue;
            }

            if (chdir(args[1]) < 0) perror("cd");
            free(copy);
            continue;
        }

        pid_t child = fork();
        if (child < 0)
        {
            perror("fork");
            return 1;
        }

        if (child == 0) { execute_command(cmd.view()); }

        if (waitpid(child, NULL, 0) < 0)
        {
            perror("waitpid");
            return 1;
        }
    }

    return 0;
}