yash.c

/* Yash: yet another shell */
/* yash.c: basic functions of the shell */
/* (C) 2007-2025 magicant */

/* This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 2 of the License, or
 * (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.  */


#include "common.h"
#include "yash.h"
#include <assert.h>
#include <errno.h>
#include <fcntl.h>
#if HAVE_GETTEXT
# include <libintl.h>
#endif
#include <locale.h>
#include <signal.h>
#include <stdbool.h>
#if HAVE_RLIMIT
# include <stdint.h>
#endif
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#if HAVE_RLIMIT
# include <sys/time.h>
# include <sys/resource.h>
#endif
#include <unistd.h>
#include <wchar.h>
#include "alias.h"
#include "builtin.h"
#include "configm.h"
#include "exec.h"
#include "expand.h"
#if YASH_ENABLE_HISTORY
# include "history.h"
#endif
#include "input.h"
#include "job.h"
#include "option.h"
#include "parser.h"
#include "path.h"
#include "redir.h"
#include "sig.h"
#include "strbuf.h"
#include "util.h"
#include "variable.h"


extern int main(int argc, char **argv)
    __attribute__((nonnull));
static struct input_file_info_T *new_input_file_info(int fd, size_t bufsize)
    __attribute__((malloc,warn_unused_result));
static void execute_profile(const wchar_t *profile);
static void execute_rcfile(const wchar_t *rcfile);
static bool execute_file_in(const wchar_t *dir_var_name, const wchar_t *path)
    __attribute__((nonnull));
static bool execute_file(const wchar_t *path);
static bool execute_file_mbs(const char *path);
static void maybe_raise(int signal);
static void print_help(void);
static void print_version(void);

static void parse_and_exec(struct parseparam_T *pinfo, bool finally_exit)
    __attribute__((nonnull(1)));
static bool input_is_interactive_terminal(const parseparam_T *pinfo)
    __attribute__((nonnull));

/* The process ID of the shell.
 * This value does not change in a subshell. */
pid_t shell_pid;
/* The process group ID of the shell.
 * In a job-controlled subshell, this value is set to the subshell's pgid. */
pid_t shell_pgid;

/* Set to true when the shell has been initialized. */
bool shell_initialized;
/* Set to true in a subshell. */
bool is_subshell;

/* If this flag is true when the "exit" built-in is invoked, the -f option is
 * assumed to be specified. */
static bool forceexit;
/* The next value of `forceexit'. */
bool nextforceexit;

/* The `input_file_info_T' structure for reading from the standard input. */
struct input_file_info_T *stdin_input_file_info;


/* The "main" function. The execution of the shell starts here. */
int main(int argc, char **argv)
{
    void *wargv[argc + 1];
    const wchar_t *shortest_name;

    setvbuf(stdout, NULL, _IOLBF, BUFSIZ);
    setvbuf(stderr, NULL, _IOLBF, BUFSIZ);

    setlocale(LC_ALL, "");
#if HAVE_GETTEXT
    bindtextdomain(PACKAGE_NAME, LOCALEDIR);
    textdomain(PACKAGE_NAME);
#endif

    /* convert arguments into wide strings */
    for (int i = 0; i < argc; i++) {
        wargv[i] = malloc_mbstowcs(argv[i]);
        if (wargv[i] == NULL) {
            fprintf(stderr,
                    gt("%s: cannot convert the argument `%s' "
                        "into a wide character string"),
                    argv[0], argv[i]);
            fprintf(stderr,
                    gt("%s: the argument is replaced with an empty string\n"),
                    argv[0]);
            wargv[i] = xwcsdup(L"");
        }
    }
    wargv[argc] = NULL;

    /* parse argv[0] */
    yash_program_invocation_name = wargv[0] != NULL ? wargv[0] : L"";
    yash_program_invocation_short_name
        = wcsrchr(yash_program_invocation_name, L'/');
    if (yash_program_invocation_short_name != NULL)
        yash_program_invocation_short_name++;
    else
        yash_program_invocation_short_name = yash_program_invocation_name;
    command_name = yash_program_invocation_name;
    is_login_shell = (yash_program_invocation_name[0] == L'-');
    shortest_name = yash_program_invocation_short_name;
    if (shortest_name[0] == L'-')
        shortest_name++;
    if (wcscmp(shortest_name, L"sh") == 0)
        posixly_correct = true;

    shell_pid = getpid();
    shell_pgid = getpgrp();
    stdin_input_file_info = new_input_file_info(STDIN_FILENO, 1);
    init_cmdhash();
    init_homedirhash();
    init_environment();
    init_signal();
    init_shellfds();
    init_job();
    init_builtin();
    init_alias();

    struct shell_invocation_T options = {
        .profile = NULL, .rcfile = NULL,
    };

    int optresult = parse_shell_options(argc, wargv, &options);
    if (optresult != Exit_SUCCESS)
        _Exit(optresult);
    if (options.version)
        print_version();
    if (options.help)
        print_help();
    if (options.version || options.help)
        _Exit(yash_error_message_count == 0 ? Exit_SUCCESS : Exit_FAILURE);

    init_variables();

    union {
        wchar_t *command;
        int fd;
    } input;
    const char *inputname;

    if (shopt_cmdline && shopt_stdin)
        _Exit(mutually_exclusive_option_error(L'c', L's'));

    if (shopt_cmdline) {
        input.command = wargv[xoptind++];
        if (input.command == NULL) {
            xerror(0, Ngt("the -c option is specified "
                        "but no command is given"));
            _Exit(Exit_ERROR);
        }
        if (xoptind < argc) {
            inputname = argv[xoptind];
            command_name = wargv[xoptind++];
        } else {
            inputname = posixly_correct ? "sh -c" : "yash -c";
        }
    } else {
        if (argc == xoptind)
            shopt_stdin = true;
        if (shopt_stdin) {
            input.fd = STDIN_FILENO;
            inputname = NULL;
            if (!options.is_interactive_set
                    && isatty(STDIN_FILENO) && isatty(STDERR_FILENO))
                is_interactive = true;
            unset_nonblocking(STDIN_FILENO);
        } else {
            inputname = argv[xoptind];
            command_name = wargv[xoptind];
            xoptind++;
            input.fd = move_to_shellfd(open(inputname, O_RDONLY));
            if (input.fd < 0) {
                int errno_ = errno;
                xerror(errno_, Ngt("cannot open file `%s'"), inputname);
                _Exit(errno_ == ENOENT ? Exit_NOTFOUND : Exit_NOEXEC);
            }
        }
    }

#if YASH_ENABLE_LINEEDIT
    /* enable line editing if interactive and connected to a terminal */
    if (!options.lineedit_set && shopt_lineedit == SHOPT_NOLINEEDIT)
        if (is_interactive && isatty(STDIN_FILENO) && isatty(STDERR_FILENO))
            set_lineedit_option(SHOPT_VI);
#endif

    if (!options.do_job_control_set)
        do_job_control = is_interactive;
    if (do_job_control) {
        open_ttyfd();
        ensure_foreground();
    }
    set_signals();
    set_positional_parameters(&wargv[xoptind]);

    if (is_login_shell && !posixly_correct && !options.noprofile)
        if (getuid() == geteuid() && getgid() == getegid())
            execute_profile(options.profile);
    if (is_interactive && !options.norcfile)
        if (getuid() == geteuid() && getgid() == getegid())
            execute_rcfile(options.rcfile);

    shell_initialized = true;

    if (shopt_cmdline)
        exec_wcs(input.command, inputname, true);
    else
        exec_input(input.fd, inputname, XIO_SUBST_ALIAS | XIO_FINALLY_EXIT |
                (is_interactive ? XIO_INTERACTIVE : 0));

    assert(false);
}

struct input_file_info_T *new_input_file_info(int fd, size_t bufsize)
{
    struct input_file_info_T *info
        = xmallocs(sizeof *info, bufsize, sizeof *info->buf);
    info->fd = fd;
    info->bufpos = info->bufmax = 0;
    info->bufsize = bufsize;
    memset(&info->state, 0, sizeof info->state);  // initial shift state
    return info;
}

/* Executes "$XDG_CONFIG_HOME/yash/profile", "$HOME/.config/yash/profile" or
 * "$HOME/.yash_profile" as a fallback.
 */
void execute_profile(const wchar_t *profile)
{
    if (profile != NULL) {
        execute_file(profile);
        return;
    }

    if (execute_file_in(L VAR_XDG_CONFIG_HOME, L"yash/profile"))
        return;

    if (execute_file_in(L VAR_HOME, L".config/yash/profile"))
        return;

    execute_file_in(L VAR_HOME, L".yash_profile");

}


/* Executes the initialization file. `rcfile' is the filename to source.
 * If `rcfile' is NULL, defaults to "$XDG_CONFIG_HOME/yash/rc",
 * "~/.config/yash/rc", or "~/.yashrc" as a fallback and * finally if the file
 * cannot * be read it falls back to "initialization/default" * from
 * $YASH_LOADPATH. * In the POSIXly-correct mode, `rcfile' is ignored and * "$ENV"
 * is used. */
void execute_rcfile(const wchar_t *rcfile)
{
    if (posixly_correct) {
        const wchar_t *env = getvar(L VAR_ENV);
        if (env == NULL)
            return;
        wchar_t *path = parse_and_expand_string(env, "$ENV", false);
        execute_file(path);
        free(path);
        return;
    }

    if (rcfile != NULL) {
        execute_file(rcfile);
        return;
    }

    if (execute_file_in(L VAR_XDG_CONFIG_HOME, L"yash/rc"))
        return;

    if (execute_file_in(L VAR_HOME, L".config/yash/rc"))
        return;

    if (execute_file_in(L VAR_HOME, L".yashrc"))
        return;

    char *path = which("initialization/default", get_path_array(PA_LOADPATH),
            is_readable_regular);
    execute_file_mbs(path);
    free(path);
}

/* Executes the specified file. The `path' must be relative to $HOME. */
bool execute_file_in(const wchar_t *dir_var_name, const wchar_t *path)
{
    const wchar_t *directory = getvar(dir_var_name);
    if (directory == NULL || directory[0] == L'\0')
        return false;

    xwcsbuf_T fullpath;
    wb_initwithmax(&fullpath, add(add(wcslen(directory), wcslen(path)), 1));
    wb_cat(&fullpath, directory);
    if (fullpath.contents[fullpath.length - 1] != L'/')
        wb_wccat(&fullpath, L'/');
    wb_cat(&fullpath, path);

    bool executed = execute_file(fullpath.contents);

    wb_destroy(&fullpath);

    return executed;
}

/* Executes the specified file if `path' is non-NULL.
 * Returns true iff the file was found. */
bool execute_file(const wchar_t *path)
{
    if (path == NULL)
        return false;

    char *mbspath = malloc_wcstombs(path);
    bool executed = execute_file_mbs(mbspath);
    free(mbspath);
    return executed;
}

/* Executes the specified file if `path' is non-NULL.
 * Returns true iff the file was found. */
bool execute_file_mbs(const char *path)
{
    if (path == NULL)
        return false;

    int fd = move_to_shellfd(open(path, O_RDONLY));
    if (fd < 0)
        return false;

    exec_input(fd, path, XIO_SUBST_ALIAS);
    cancel_return();
    remove_shellfd(fd);
    xclose(fd);
    return true;
}

/* Exits the shell with the specified exit status.
 * When this function is first called and `status' is negative, the value of
 * `laststatus' is used for `status'. When this function is called again and
 * `status' is negative, the value for the first call is used.
 * This function executes the EXIT trap.
 * This function never returns.
 * This function is reentrant and exits immediately if reentered.
 * If the exit status is a value that is returned when a command process is
 * killed by a signal, the shell kills itself with the same signal instead of
 * exiting with the exit status. */
void exit_shell_with_status(int status)
{
    if (status >= 0)
        laststatus = status;
    assert(laststatus >= 0);

    if (exitstatus < 0) {
        /* We're not executing the EXIT trap, so execute it now. */
        if (status >= 0)
            exitstatus = status;
        else if (savelaststatus >= 0)
            exitstatus = savelaststatus;
        else
            exitstatus = laststatus;
        execute_exit_trap();
    } else {
        /* We're already executing the EXIT trap, so avoid executing it
         * recursively. */
        if (status >= 0)
            exitstatus = status;
    }

#if YASH_ENABLE_HISTORY
    finalize_history();
#endif

    if (exitstatus > TERMSIGOFFSET) {
        int signal = exitstatus - TERMSIGOFFSET;
        maybe_raise(signal);
    }

    assert(exitstatus >= 0);
    _Exit(exitstatus);
}

/* Kills the current shell process with the specified signal.
 * This function does not return if the process is actually killed.
 * This function may return if the process is not killed, for example, if
 * the signal is not fatal. */
/* This function requires the setrlimit function. Without it, the signal may
 * generate a core dump, which is not desired. This function does nothing if
 * setrlimit is not available. */
void maybe_raise(int signal)
{
    switch (signal) {
        case SIGSTOP:
        case SIGTSTP:
        case SIGTTIN:
        case SIGTTOU:
        case SIGCONT:
        case SIGCHLD:
        case SIGURG:
#ifdef SIGWINCH
        case SIGWINCH:
#endif
            /* ignore these signals since they are not fatal */
            return;
    }

#if HAVE_RLIMIT
    // Disable core dump
    struct rlimit limit;
    limit.rlim_cur = limit.rlim_max = 0;
    if (setrlimit(RLIMIT_CORE, &limit) != 0)
        return;

    if (signal != SIGKILL) {
        // Reset signal disposition
        struct sigaction action;
        action.sa_handler = SIG_DFL;
        action.sa_flags = 0;
        if (sigemptyset(&action.sa_mask) != 0)
            return;
        if (sigaction(signal, &action, NULL) != 0)
            return;
    }

    // Unblock the signal
    sigset_t sigset;
    if (sigemptyset(&sigset) != 0)
        return;
    if (sigaddset(&sigset, signal) != 0)
        return;
    if (sigprocmask(SIG_UNBLOCK, &sigset, NULL) != 0)
        return;

    raise(signal);
#endif /* HAVE_RLIMIT */
}

/* Prints the help message to the standard output. */
void print_help(void)
{
#if YASH_ENABLE_HELP
    const char *shell_name = posixly_correct ? "sh" : "yash";
    xprintf(gt(
            "Syntax:\n"
            "\t%s [option...] [filename [argument...]]\n"
            "\t%s [option...] -c command [command_name [argument...]]\n"
            "\t%s [option...] -s [argument...]\n"),
            shell_name, shell_name, shell_name);

    xprintf("\n");

    print_shopts(true);

    xprintf(gt("Try `man yash' for details.\n"));
#endif /* YASH_ENABLE_HELP */
}

/* Prints the version info to the standard output. */
void print_version(void)
{
    xprintf(gt("Yet another shell, version %s\n"), PACKAGE_VERSION);
    xprintf(PACKAGE_COPYRIGHT "\n");
    xprintf(gt("This is free software licensed under GNU GPL version 2.\n"
            "You can modify and redistribute it, but there is NO WARRANTY.\n"));

    if (shopt_verbose) {
        xprintf(gt("\nEnabled features:\n"));
        xprintf(""
#ifndef NDEBUG
                " * DEBUG\n"
#endif
#if YASH_ENABLE_ARRAY
                " * array\n"
#endif
#if YASH_ENABLE_DIRSTACK
                " * dirstack\n"
#endif
#if YASH_ENABLE_HELP
                " * help\n"
#endif
#if YASH_ENABLE_HISTORY
                " * history\n"
#endif
#if YASH_ENABLE_LINEEDIT
                " * lineedit\n"
#endif
#if HAVE_GETTEXT
                " * nls\n"
#endif
#if YASH_ENABLE_PRINTF
                " * printf/echo\n"
#endif
#if YASH_ENABLE_SOCKET
                " * socket\n"
#endif
#if YASH_ENABLE_TEST
                " * test\n"
#endif
#if YASH_ENABLE_ULIMIT
                " * ulimit\n"
#endif
              );
    }
}


/********** Functions to Execute Commands **********/

/* Parses the specified wide string and executes it as commands.
 * `name' is printed in an error message on syntax error. `name' may be NULL.
 * If there are no commands in `code', `laststatus' is set to zero. */
void exec_wcs(const wchar_t *code, const char *name, bool finally_exit)
{
    struct input_wcs_info_T iinfo = {
        .src = code,
    };
    struct parseparam_T pinfo = {
        .print_errmsg = true,
        .enable_verbose = false,
        .enable_alias = true,
        .filename = name,
        .lineno = 1,
        .input = input_wcs,
        .inputinfo = &iinfo,
        .interactive = false,
        .is_dot_builtin = false,
    };

    parse_and_exec(&pinfo, finally_exit);
}

/* Parses the input from the specified file descriptor and executes commands.
 * The file descriptor must be either STDIN_FILENO or a shell FD. If the file
 * descriptor is STDIN_FILENO, XIO_FINALLY_EXIT must be specified in `options'.
 * If `name' is non-NULL, it is printed in an error message on syntax error.
 * If XIO_INTERACTIVE is specified, the input is considered interactive.
 * If there are no commands in the input, `laststatus' is set to zero. */
void exec_input(int fd, const char *name, exec_input_options_T options)
{
    struct parseparam_T pinfo = {
        .print_errmsg = true,
        .enable_verbose = true,
        .enable_alias = options & XIO_SUBST_ALIAS,
        .filename = name,
        .lineno = 1,
        .interactive = options & XIO_INTERACTIVE,
        .is_dot_builtin = options & XIO_DOT_BUILTIN,
    };
    struct input_interactive_info_T intrinfo;
    struct input_file_info_T *inputinfo;

    if (fd == STDIN_FILENO)
        inputinfo = stdin_input_file_info;
    else
        inputinfo = new_input_file_info(fd, BUFSIZ);

    if (pinfo.interactive) {
        intrinfo.fileinfo = inputinfo;
        intrinfo.prompttype = 1;
        pinfo.input = input_interactive;
        pinfo.inputinfo = &intrinfo;
    } else {
        pinfo.input = input_file;
        pinfo.inputinfo = inputinfo;
    }
    parse_and_exec(&pinfo, options & XIO_FINALLY_EXIT);

    assert(inputinfo != stdin_input_file_info);
    free(inputinfo);
}

/* Parses the input using the specified `parseparam_T' and executes commands.
 * If no commands were executed, `laststatus' is set to Exit_SUCCESS. */
void parse_and_exec(parseparam_T *pinfo, bool finally_exit)
{
    bool executed = false;

    if (pinfo->interactive)
        disable_return();

    for (;;) {
        if (pinfo->interactive) {
            set_laststatus_if_interrupted();
            uncancel_current_command();
            forceexit = nextforceexit;
            nextforceexit = false;
            pinfo->lineno = 1;
        } else {
            if (need_break())
                goto out;
        }

        and_or_T *commands;
        switch (read_and_parse(pinfo, &commands)) {
            case PR_OK:
                if (commands != NULL) {
                    if (shopt_exec || is_interactive) {
                        exec_and_or_lists(commands,
                                finally_exit && !pinfo->interactive &&
                                pinfo->lastinputresult == INPUT_EOF);
                        executed = true;
                    }
                    andorsfree(commands);
                }
                break;
            case PR_EOF:
                if (!executed)
                    laststatus = Exit_SUCCESS;
                if (!finally_exit)
                    goto out;
                if (shopt_ignoreeof && input_is_interactive_terminal(pinfo)) {
                    fprintf(stderr, gt("Use `exit' to leave the shell.\n"));
                } else {
                    wchar_t argv0[] = L"EOF";
                    exit_builtin(1, (void *[]) { argv0, NULL });
                }
                break;
            case PR_SYNTAX_ERROR:
                if (shell_initialized && !is_interactive_now)
                    exit_shell_with_status(Exit_SYNERROR);
                if (!pinfo->interactive) {
                    laststatus = Exit_SYNERROR;
                    goto out;
                }
                break;
            case PR_INPUT_ERROR:
                laststatus = pinfo->is_dot_builtin ? Exit_ERROR : Exit_INPUTERR;
                goto out;
        }
    }
out:
    if (finally_exit)
        exit_shell();
}

bool input_is_interactive_terminal(const parseparam_T *pinfo)
{
    if (!pinfo->interactive)
        return false;

    struct input_interactive_info_T *ir = pinfo->inputinfo;
    return isatty(ir->fileinfo->fd);
}


/********** Built-ins **********/

/* Options for the "exit" and "suspend" built-ins. */
const struct xgetopt_T force_help_options[] = {
    { L'f', L"force", OPTARG_NONE, true,  NULL, },
#if YASH_ENABLE_HELP
    { L'-', L"help",  OPTARG_NONE, false, NULL, },
#endif
    { L'\0', NULL, 0, false, NULL, },
};

/* The "exit" built-in.
 * If the shell is interactive, there are stopped jobs and the -f flag is not
 * specified, then prints a warning message and does not exit. */
int exit_builtin(int argc, void **argv)
{
    const struct xgetopt_T *opt;
    xoptind = 0;
    while ((opt = xgetopt(argv, force_help_options, 0)) != NULL) {
        switch (opt->shortopt) {
            case L'f':
                forceexit = true;
                break;
#if YASH_ENABLE_HELP
            case L'-':
                return print_builtin_help(ARGV(0));
#endif
            default:
                return special_builtin_error(Exit_ERROR);
        }
    }

    if (!validate_operand_count(argc - xoptind, 0, 1))
        return special_builtin_error(Exit_ERROR);

    size_t sjc;
    if (is_interactive_now && !forceexit && (sjc = stopped_job_count()) > 0) {
        fprintf(stderr,
                ngt("You have a stopped job!",
                    "You have %zu stopped jobs!",
                    sjc),
                sjc);
        fprintf(stderr, gt("  Use `exit' again to exit anyway.\n"));
        forceexit = nextforceexit = true;
        return Exit_FAILURE;
    }

    int status;
    const wchar_t *statusstr = ARGV(xoptind);
    if (statusstr != NULL) {
        if (!xwcstoi(statusstr, 10, &status) || status < 0) {
            xerror(0, Ngt("`%ls' is not a valid integer"), statusstr);
            status = Exit_ERROR;
            special_builtin_error(status);
        }
    } else {
        status = -1;
    }
    exit_shell_with_status(status);
    assert(false);
}

#if YASH_ENABLE_HELP
const char exit_help[] = Ngt(
"exit the shell"
);
const char exit_syntax[] = Ngt(
"\texit [-f] [exit_status]\n"
);
#endif

/* The "suspend" built-in, which accepts the following options:
 *  -f: suspend even if it may cause a deadlock. */
int suspend_builtin(int argc, void **argv)
{
    bool force = false;

    const struct xgetopt_T *opt;
    xoptind = 0;
    while ((opt = xgetopt(argv, force_help_options, 0)) != NULL) {
        switch (opt->shortopt) {
            case L'f':
                force = true;
                break;
#if YASH_ENABLE_HELP
            case L'-':
                return print_builtin_help(ARGV(0));
#endif
            default:
                return Exit_ERROR;
        }
    }

    if (argc != xoptind)
        return too_many_operands_error(0);

    if (!force && is_interactive_now && getsid(0) == shell_pgid) {
        xerror(0, Ngt("refusing to suspend because of a possible deadlock.\n"
                    "Use the -f option to suspend anyway."));
        return Exit_FAILURE;
    }

    stop_myself();

    if (doing_job_control_now)
        ensure_foreground();
    return (yash_error_message_count == 0) ? Exit_SUCCESS : Exit_FAILURE;
}

#if YASH_ENABLE_HELP
const char suspend_help[] = Ngt(
"suspend the shell"
);
const char suspend_syntax[] = Ngt(
"\tsuspend [-f]\n"
);
#endif


/* vim: set ts=8 sts=4 sw=4 et tw=80: */