path: root/js/src/shell/OSObject.cpp

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 * vim: set ts=8 sts=4 et sw=4 tw=99:
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

// OSObject.h - os object for exposing posix system calls in the JS shell

#include "shell/OSObject.h"

#include <errno.h>
#include <stdlib.h>
#ifdef XP_WIN
#include <direct.h>
#include <process.h>
#include <string.h>
#else
#include <sys/wait.h>
#include <unistd.h>
#endif

#include "jsapi.h"
// For JSFunctionSpecWithHelp
#include "jsfriendapi.h"
#include "jsobj.h"
#ifdef XP_WIN
# include "jswin.h"
#endif
#include "jswrapper.h"

#include "js/Conversions.h"
#include "shell/jsshell.h"
#include "vm/StringBuffer.h"
#include "vm/TypedArrayObject.h"

#include "jsobjinlines.h"

#ifdef XP_WIN
# define PATH_MAX (MAX_PATH > _MAX_DIR ? MAX_PATH : _MAX_DIR)
# define getcwd _getcwd
#else
# include <libgen.h>
#endif

using js::shell::RCFile;

static RCFile** gErrFilePtr = nullptr;
static RCFile** gOutFilePtr = nullptr;

namespace js {
namespace shell {

#ifdef XP_WIN
const char PathSeparator = '\\';
#else
const char PathSeparator = '/';
#endif

static bool
IsAbsolutePath(const JSAutoByteString& filename)
{
    const char* pathname = filename.ptr();

    if (pathname[0] == PathSeparator)
        return true;

#ifdef XP_WIN
    // On Windows there are various forms of absolute paths (see
    // http://msdn.microsoft.com/en-us/library/windows/desktop/aa365247%28v=vs.85%29.aspx
    // for details):
    //
    //   "\..."
    //   "\\..."
    //   "C:\..."
    //
    // The first two cases are handled by the test above so we only need a test
    // for the last one here.

    if ((strlen(pathname) > 3 &&
        isalpha(pathname[0]) && pathname[1] == ':' && pathname[2] == '\\'))
    {
        return true;
    }
#endif

    return false;
}

/*
 * Resolve a (possibly) relative filename to an absolute path. If
 * |scriptRelative| is true, then the result will be relative to the directory
 * containing the currently-running script, or the current working directory if
 * the currently-running script is "-e" (namely, you're using it from the
 * command line.) Otherwise, it will be relative to the current working
 * directory.
 */
JSString*
ResolvePath(JSContext* cx, HandleString filenameStr, PathResolutionMode resolveMode)
{
    if (!filenameStr) {
#ifdef XP_WIN
        return JS_NewStringCopyZ(cx, "nul");
#else
        return JS_NewStringCopyZ(cx, "/dev/null");
#endif
    }

    JSAutoByteString filename(cx, filenameStr);
    if (!filename)
        return nullptr;

    if (IsAbsolutePath(filename))
        return filenameStr;

    /* Get the currently executing script's name. */
    JS::AutoFilename scriptFilename;
    if (!DescribeScriptedCaller(cx, &scriptFilename))
        return nullptr;

    if (!scriptFilename.get())
        return nullptr;

    if (strcmp(scriptFilename.get(), "-e") == 0 || strcmp(scriptFilename.get(), "typein") == 0)
        resolveMode = RootRelative;

    char buffer[PATH_MAX+1];
    if (resolveMode == ScriptRelative) {
#ifdef XP_WIN
        // The docs say it can return EINVAL, but the compiler says it's void
        _splitpath(scriptFilename.get(), nullptr, buffer, nullptr, nullptr);
#else
        strncpy(buffer, scriptFilename.get(), PATH_MAX+1);
        if (buffer[PATH_MAX] != '\0')
            return nullptr;

        // dirname(buffer) might return buffer, or it might return a
        // statically-allocated string
        memmove(buffer, dirname(buffer), strlen(buffer) + 1);
#endif
    } else {
        const char* cwd = getcwd(buffer, PATH_MAX);
        if (!cwd)
            return nullptr;
    }

    size_t len = strlen(buffer);
    buffer[len] = '/';
    strncpy(buffer + len + 1, filename.ptr(), sizeof(buffer) - (len+1));
    if (buffer[PATH_MAX] != '\0')
        return nullptr;

    return JS_NewStringCopyZ(cx, buffer);
}

JSObject*
FileAsTypedArray(JSContext* cx, JS::HandleString pathnameStr)
{
    JSAutoByteString pathname(cx, pathnameStr);
    if (!pathname)
        return nullptr;

    FILE* file = fopen(pathname.ptr(), "rb");
    if (!file) {
        /*
         * Use Latin1 variant here because the encoding of the return value of
         * strerror function can be non-UTF-8.
         */
        JS_ReportErrorLatin1(cx, "can't open %s: %s", pathname.ptr(), strerror(errno));
        return nullptr;
    }
    AutoCloseFile autoClose(file);

    RootedObject obj(cx);
    if (fseek(file, 0, SEEK_END) != 0) {
        pathname.clear();
        if (!pathname.encodeUtf8(cx, pathnameStr))
            return nullptr;
        JS_ReportErrorUTF8(cx, "can't seek end of %s", pathname.ptr());
    } else {
        size_t len = ftell(file);
        if (fseek(file, 0, SEEK_SET) != 0) {
            pathname.clear();
            if (!pathname.encodeUtf8(cx, pathnameStr))
                return nullptr;
            JS_ReportErrorUTF8(cx, "can't seek start of %s", pathname.ptr());
        } else {
            obj = JS_NewUint8Array(cx, len);
            if (!obj)
                return nullptr;
            js::TypedArrayObject& ta = obj->as<js::TypedArrayObject>();
            if (ta.isSharedMemory()) {
                // Must opt in to use shared memory.  For now, don't.
                //
                // (It is incorrect to read into the buffer without
                // synchronization since that can create a race.  A
                // lock here won't fix it - both sides must
                // participate.  So what one must do is to create a
                // temporary buffer, read into that, and use a
                // race-safe primitive to copy memory into the
                // buffer.)
                pathname.clear();
                if (!pathname.encodeUtf8(cx, pathnameStr))
                    return nullptr;
                JS_ReportErrorUTF8(cx, "can't read %s: shared memory buffer", pathname.ptr());
                return nullptr;
            }
            char* buf = static_cast<char*>(ta.viewDataUnshared());
            size_t cc = fread(buf, 1, len, file);
            if (cc != len) {
                if (ptrdiff_t(cc) < 0) {
                    /*
                     * Use Latin1 variant here because the encoding of the return
                     * value of strerror function can be non-UTF-8.
                     */
                    JS_ReportErrorLatin1(cx, "can't read %s: %s", pathname.ptr(), strerror(errno));
                } else {
                    pathname.clear();
                    if (!pathname.encodeUtf8(cx, pathnameStr))
                        return nullptr;
                    JS_ReportErrorUTF8(cx, "can't read %s: short read", pathname.ptr());
                }
                obj = nullptr;
            }
        }
    }
    return obj;
}

static bool
ReadFile(JSContext* cx, unsigned argc, Value* vp, bool scriptRelative)
{
    CallArgs args = CallArgsFromVp(argc, vp);

    if (args.length() < 1 || args.length() > 2) {
        JS_ReportErrorNumberASCII(cx, js::shell::my_GetErrorMessage, nullptr,
                                  args.length() < 1 ? JSSMSG_NOT_ENOUGH_ARGS : JSSMSG_TOO_MANY_ARGS,
                                  "snarf");
        return false;
    }

    if (!args[0].isString() || (args.length() == 2 && !args[1].isString())) {
        JS_ReportErrorNumberASCII(cx, js::shell::my_GetErrorMessage, nullptr, JSSMSG_INVALID_ARGS,
                                  "snarf");
        return false;
    }

    RootedString givenPath(cx, args[0].toString());
    RootedString str(cx, js::shell::ResolvePath(cx, givenPath, scriptRelative ? ScriptRelative : RootRelative));
    if (!str)
        return false;

    if (args.length() > 1) {
        JSString* opt = JS::ToString(cx, args[1]);
        if (!opt)
            return false;
        bool match;
        if (!JS_StringEqualsAscii(cx, opt, "binary", &match))
            return false;
        if (match) {
            JSObject* obj;
            if (!(obj = FileAsTypedArray(cx, str)))
                return false;
            args.rval().setObject(*obj);
            return true;
        }
    }

    if (!(str = FileAsString(cx, str)))
        return false;
    args.rval().setString(str);
    return true;
}

static bool
osfile_readFile(JSContext* cx, unsigned argc, Value* vp)
{
    return ReadFile(cx, argc, vp, false);
}

static bool
osfile_readRelativeToScript(JSContext* cx, unsigned argc, Value* vp)
{
    return ReadFile(cx, argc, vp, true);
}

static bool
osfile_writeTypedArrayToFile(JSContext* cx, unsigned argc, Value* vp)
{
    CallArgs args = CallArgsFromVp(argc, vp);

    if (args.length() != 2 ||
        !args[0].isString() ||
        !args[1].isObject() ||
        !args[1].toObject().is<TypedArrayObject>())
    {
        JS_ReportErrorNumberASCII(cx, my_GetErrorMessage, nullptr, JSSMSG_INVALID_ARGS,
                                  "writeTypedArrayToFile");
        return false;
    }

    RootedString givenPath(cx, args[0].toString());
    RootedString str(cx, ResolvePath(cx, givenPath, RootRelative));
    if (!str)
        return false;

    JSAutoByteString filename(cx, str);
    if (!filename)
        return false;

    FILE* file = fopen(filename.ptr(), "wb");
    if (!file) {
        /*
         * Use Latin1 variant here because the encoding of the return value of
         * strerror function can be non-UTF-8.
         */
        JS_ReportErrorLatin1(cx, "can't open %s: %s", filename.ptr(), strerror(errno));
        return false;
    }
    AutoCloseFile autoClose(file);

    TypedArrayObject* obj = &args[1].toObject().as<TypedArrayObject>();

    if (obj->isSharedMemory()) {
        // Must opt in to use shared memory.  For now, don't.
        //
        // See further comments in FileAsTypedArray, above.
        filename.clear();
        if (!filename.encodeUtf8(cx, str))
            return false;
        JS_ReportErrorUTF8(cx, "can't write %s: shared memory buffer", filename.ptr());
        return false;
    }
    void* buf = obj->viewDataUnshared();
    if (fwrite(buf, obj->bytesPerElement(), obj->length(), file) != obj->length() ||
        !autoClose.release())
    {
        filename.clear();
        if (!filename.encodeUtf8(cx, str))
            return false;
        JS_ReportErrorUTF8(cx, "can't write %s", filename.ptr());
        return false;
    }

    args.rval().setUndefined();
    return true;
}

/* static */ RCFile*
RCFile::create(JSContext* cx, const char* filename, const char* mode)
{
    FILE* fp = fopen(filename, mode);
    if (!fp)
        return nullptr;

    RCFile* file = cx->new_<RCFile>(fp);
    if (!file) {
        fclose(fp);
        return nullptr;
    }

    return file;
}

void
RCFile::close()
{
    if (fp)
        fclose(fp);
    fp = nullptr;
}

bool
RCFile::release()
{
    if (--numRefs)
        return false;
    this->close();
    return true;
}

class FileObject : public JSObject {
    enum : uint32_t {
        FILE_SLOT = 0,
        NUM_SLOTS
    };

  public:
    static const js::Class class_;

    static FileObject* create(JSContext* cx, RCFile* file) {
        JSObject* obj = js::NewObjectWithClassProto(cx, &class_, nullptr);
        if (!obj)
            return nullptr;

        FileObject* fileObj = &obj->as<FileObject>();
        fileObj->setRCFile(file);
        file->acquire();
        return fileObj;
    }

    static void finalize(FreeOp* fop, JSObject* obj) {
        FileObject* fileObj = &obj->as<FileObject>();
        RCFile* file = fileObj->rcFile();
        if (file->release()) {
            fileObj->setRCFile(nullptr);
            fop->delete_(file);
        }
    }

    bool isOpen() {
        RCFile* file = rcFile();
        return file && file->isOpen();
    }

    void close() {
        if (!isOpen())
            return;
        rcFile()->close();
    }

    RCFile* rcFile() {
        return reinterpret_cast<RCFile*>(js::GetReservedSlot(this, FILE_SLOT).toPrivate());
    }

  private:

    void setRCFile(RCFile* file) {
        js::SetReservedSlot(this, FILE_SLOT, PrivateValue(file));
    }
};

static const js::ClassOps FileObjectClassOps = {
    nullptr,               /* addProperty */
    nullptr,               /* delProperty */
    nullptr,               /* getProperty */
    nullptr,               /* setProperty */
    nullptr,               /* enumerate */
    nullptr,               /* resolve */
    nullptr,               /* mayResolve */
    FileObject::finalize,  /* finalize */
    nullptr,               /* call */
    nullptr,               /* hasInstance */
    nullptr,               /* construct */
    nullptr                /* trace */
};

const js::Class FileObject::class_ = {
    "File",
    JSCLASS_HAS_RESERVED_SLOTS(FileObject::NUM_SLOTS) |
    JSCLASS_FOREGROUND_FINALIZE,
    &FileObjectClassOps
};

static FileObject*
redirect(JSContext* cx, HandleString relFilename, RCFile** globalFile)
{
    RootedString filename(cx, ResolvePath(cx, relFilename, RootRelative));
    if (!filename)
        return nullptr;
    JSAutoByteString filenameABS(cx, filename);
    if (!filenameABS)
        return nullptr;
    RCFile* file = RCFile::create(cx, filenameABS.ptr(), "wb");
    if (!file) {
        /*
         * Use Latin1 variant here because the encoding of the return value of
         * strerror function can be non-UTF-8.
         */
        JS_ReportErrorLatin1(cx, "cannot redirect to %s: %s", filenameABS.ptr(), strerror(errno));
        return nullptr;
    }

    // Grant the global gOutFile ownership of the new file, release ownership
    // of its old file, and return a FileObject owning the old file.
    file->acquire(); // Global owner of new file

    FileObject* fileObj = FileObject::create(cx, *globalFile); // Newly created owner of old file
    if (!fileObj) {
        file->release();
        return nullptr;
    }

    (*globalFile)->release(); // Release (global) ownership of old file.
    *globalFile = file;

    return fileObj;
}

static bool
Redirect(JSContext* cx, const CallArgs& args, RCFile** outFile)
{
    if (args.length() > 1) {
        JS_ReportErrorNumberASCII(cx, js::shell::my_GetErrorMessage, nullptr, JSSMSG_INVALID_ARGS,
                                  "redirect");
        return false;
    }

    RCFile* oldFile = *outFile;
    RootedObject oldFileObj(cx, FileObject::create(cx, oldFile));
    if (!oldFileObj)
        return false;

    if (args.get(0).isUndefined()) {
        args.rval().setObject(*oldFileObj);
        return true;
    }

    if (args[0].isObject()) {
        RootedObject fileObj(cx, js::CheckedUnwrap(&args[0].toObject()));
        if (!fileObj)
            return false;

        if (fileObj->is<FileObject>()) {
            // Passed in a FileObject. Create a FileObject for the previous
            // global file, and set the global file to the passed-in one.
            *outFile = fileObj->as<FileObject>().rcFile();
            (*outFile)->acquire();
            oldFile->release();

            args.rval().setObject(*oldFileObj);
            return true;
        }
    }

    RootedString filename(cx);
    if (!args[0].isNull()) {
        filename = JS::ToString(cx, args[0]);
        if (!filename)
            return false;
    }

    if (!redirect(cx, filename, outFile))
        return false;

    args.rval().setObject(*oldFileObj);
    return true;
}

static bool
osfile_redirectOutput(JSContext* cx, unsigned argc, Value* vp) {
    CallArgs args = CallArgsFromVp(argc, vp);
    return Redirect(cx, args, gOutFilePtr);
}

static bool
osfile_redirectError(JSContext* cx, unsigned argc, Value* vp) {
    CallArgs args = CallArgsFromVp(argc, vp);
    return Redirect(cx, args, gErrFilePtr);
}

static bool
osfile_close(JSContext* cx, unsigned argc, Value* vp) {
    CallArgs args = CallArgsFromVp(argc, vp);

    Rooted<FileObject*> fileObj(cx);
    if (args.get(0).isObject()) {
        JSObject *obj = js::CheckedUnwrap(&args[0].toObject());
        if (obj->is<FileObject>())
            fileObj = &obj->as<FileObject>();
    }

    if (!fileObj) {
        JS_ReportErrorNumberASCII(cx, js::shell::my_GetErrorMessage, nullptr, JSSMSG_INVALID_ARGS,
                                  "close");
        return false;
    }

    fileObj->close();

    args.rval().setUndefined();
    return true;
}

static const JSFunctionSpecWithHelp osfile_functions[] = {
    JS_FN_HELP("readFile", osfile_readFile, 1, 0,
"readFile(filename, [\"binary\"])",
"  Read filename into returned string. Filename is relative to the current\n"
               "  working directory."),

    JS_FN_HELP("readRelativeToScript", osfile_readRelativeToScript, 1, 0,
"readRelativeToScript(filename, [\"binary\"])",
"  Read filename into returned string. Filename is relative to the directory\n"
"  containing the current script."),

    JS_FS_HELP_END
};

static const JSFunctionSpecWithHelp osfile_unsafe_functions[] = {
    JS_FN_HELP("writeTypedArrayToFile", osfile_writeTypedArrayToFile, 2, 0,
"writeTypedArrayToFile(filename, data)",
"  Write the contents of a typed array to the named file."),

    JS_FN_HELP("redirect", osfile_redirectOutput, 1, 0,
"redirect([path-or-object])",
"  Redirect print() output to the named file.\n"
"   Return an opaque object representing the previous destination, which\n"
"   may be passed into redirect() later to restore the output."),

    JS_FN_HELP("redirectErr", osfile_redirectError, 1, 0,
"redirectErr([path-or-object])",
"  Same as redirect(), but for printErr"),

    JS_FN_HELP("close", osfile_close, 1, 0,
"close(object)",
"  Close the file returned by an earlier redirect call."),

    JS_FS_HELP_END
};

static bool
ospath_isAbsolute(JSContext* cx, unsigned argc, Value* vp)
{
    CallArgs args = CallArgsFromVp(argc, vp);

    if (args.length() != 1 || !args[0].isString()) {
        JS_ReportErrorNumberASCII(cx, my_GetErrorMessage, nullptr, JSSMSG_INVALID_ARGS,
                                  "isAbsolute");
        return false;
    }

    JSAutoByteString path(cx, args[0].toString());
    if (!path)
        return false;

    args.rval().setBoolean(IsAbsolutePath(path));
    return true;
}

static bool
ospath_join(JSContext* cx, unsigned argc, Value* vp)
{
    CallArgs args = CallArgsFromVp(argc, vp);

    if (args.length() < 1) {
        JS_ReportErrorNumberASCII(cx, my_GetErrorMessage, nullptr, JSSMSG_INVALID_ARGS, "join");
        return false;
    }

    // This function doesn't take into account some aspects of Windows paths,
    // e.g. the drive letter is always reset when an absolute path is appended.

    StringBuffer buffer(cx);

    for (unsigned i = 0; i < args.length(); i++) {
        if (!args[i].isString()) {
            JS_ReportErrorASCII(cx, "join expects string arguments only");
            return false;
        }

        JSAutoByteString path(cx, args[i].toString());
        if (!path)
            return false;

        if (IsAbsolutePath(path)) {
            MOZ_ALWAYS_TRUE(buffer.resize(0));
        } else if (i != 0) {
            if (!buffer.append(PathSeparator))
                return false;
        }

        if (!buffer.append(args[i].toString()))
            return false;
    }

    JSString* result = buffer.finishString();
    if (!result)
        return false;

    args.rval().setString(result);
    return true;
}

static const JSFunctionSpecWithHelp ospath_functions[] = {
    JS_FN_HELP("isAbsolute", ospath_isAbsolute, 1, 0,
"isAbsolute(path)",
"  Return whether the given path is absolute."),

    JS_FN_HELP("join", ospath_join, 1, 0,
"join(paths...)",
"  Join one or more path components in a platform independent way."),

    JS_FS_HELP_END
};

static bool
os_getenv(JSContext* cx, unsigned argc, Value* vp)
{
    CallArgs args = CallArgsFromVp(argc, vp);
    if (args.length() < 1) {
        JS_ReportErrorASCII(cx, "os.getenv requires 1 argument");
        return false;
    }
    RootedString key(cx, ToString(cx, args[0]));
    if (!key)
        return false;
    JSAutoByteString keyBytes;
    if (!keyBytes.encodeUtf8(cx, key))
        return false;

    if (const char* valueBytes = getenv(keyBytes.ptr())) {
        RootedString value(cx, JS_NewStringCopyZ(cx, valueBytes));
        if (!value)
            return false;
        args.rval().setString(value);
    } else {
        args.rval().setUndefined();
    }
    return true;
}

static bool
os_getpid(JSContext* cx, unsigned argc, Value* vp)
{
    CallArgs args = CallArgsFromVp(argc, vp);
    if (args.length() != 0) {
        JS_ReportErrorASCII(cx, "os.getpid takes no arguments");
        return false;
    }
    args.rval().setInt32(getpid());
    return true;
}

#if !defined(XP_WIN)

// There are two possible definitions of strerror_r floating around. The GNU
// one returns a char* which may or may not be the buffer you passed in. The
// other one returns an integer status code, and always writes the result into
// the provided buffer.

inline char*
strerror_message(int result, char* buffer)
{
    return result == 0 ? buffer : nullptr;
}

inline char*
strerror_message(char* result, char* buffer)
{
    return result;
}

#endif

static void
ReportSysError(JSContext* cx, const char* prefix)
{
    char buffer[200];

#if defined(XP_WIN)
    strerror_s(buffer, sizeof(buffer), errno);
    const char* errstr = buffer;
#else
    const char* errstr = strerror_message(strerror_r(errno, buffer, sizeof(buffer)), buffer);
#endif

    if (!errstr)
        errstr = "unknown error";

    size_t nbytes = strlen(prefix) + strlen(errstr) + 3;
    char* final = (char*) js_malloc(nbytes);
    if (!final) {
        JS_ReportOutOfMemory(cx);
        return;
    }

    snprintf(final, nbytes, "%s: %s", prefix, errstr);
    /*
     * Use Latin1 variant here because the encoding of the return value of
     * strerror_s and strerror_r function can be non-UTF-8.
     */
    JS_ReportErrorLatin1(cx, "%s", final);
    js_free(final);
}

static bool
os_system(JSContext* cx, unsigned argc, Value* vp)
{
    CallArgs args = CallArgsFromVp(argc, vp);

    if (args.length() == 0) {
        JS_ReportErrorASCII(cx, "os.system requires 1 argument");
        return false;
    }

    JSString* str = JS::ToString(cx, args[0]);
    if (!str)
        return false;

    JSAutoByteString command(cx, str);
    if (!command)
        return false;

    int result = system(command.ptr());
    if (result == -1) {
        ReportSysError(cx, "system call failed");
        return false;
    }

    args.rval().setInt32(result);
    return true;
}

#ifndef XP_WIN
static bool
os_spawn(JSContext* cx, unsigned argc, Value* vp)
{
    CallArgs args = CallArgsFromVp(argc, vp);

    if (args.length() == 0) {
        JS_ReportErrorASCII(cx, "os.spawn requires 1 argument");
        return false;
    }

    JSString* str = JS::ToString(cx, args[0]);
    if (!str)
        return false;

    JSAutoByteString command(cx, str);
    if (!command)
        return false;

    int32_t childPid = fork();
    if (childPid == -1) {
        ReportSysError(cx, "fork failed");
        return false;
    }

    if (childPid) {
        args.rval().setInt32(childPid);
        return true;
    }

    // We are in the child

    const char* cmd[] = {"sh", "-c", nullptr, nullptr};
    cmd[2] = command.ptr();

    execvp("sh", (char * const*)cmd);
    exit(1);
}

static bool
os_kill(JSContext* cx, unsigned argc, Value* vp)
{
    CallArgs args = CallArgsFromVp(argc, vp);
    int32_t pid;
    if (args.length() < 1) {
        JS_ReportErrorASCII(cx, "os.kill requires 1 argument");
        return false;
    }
    if (!JS::ToInt32(cx, args[0], &pid))
        return false;

    // It is too easy to kill yourself accidentally with os.kill("goose").
    if (pid == 0 && !args[0].isInt32()) {
        JS_ReportErrorASCII(cx, "os.kill requires numeric pid");
        return false;
    }

    int signal = SIGINT;
    if (args.length() > 1) {
        if (!JS::ToInt32(cx, args[1], &signal))
            return false;
    }

    int status = kill(pid, signal);
    if (status == -1) {
        ReportSysError(cx, "kill failed");
        return false;
    }

    args.rval().setUndefined();
    return true;
}

static bool
os_waitpid(JSContext* cx, unsigned argc, Value* vp)
{
    CallArgs args = CallArgsFromVp(argc, vp);

    int32_t pid;
    if (args.length() == 0) {
        pid = -1;
    } else {
        if (!JS::ToInt32(cx, args[0], &pid))
            return false;
    }

    bool nohang = false;
    if (args.length() >= 2)
        nohang = JS::ToBoolean(args[1]);

    int status = 0;
    pid_t result = waitpid(pid, &status, nohang ? WNOHANG : 0);
    if (result == -1) {
        ReportSysError(cx, "os.waitpid failed");
        return false;
    }

    RootedObject info(cx, JS_NewPlainObject(cx));
    if (!info)
        return false;

    RootedValue v(cx);
    if (result != 0) {
        v.setInt32(result);
        if (!JS_DefineProperty(cx, info, "pid", v, JSPROP_ENUMERATE))
            return false;
        if (WIFEXITED(status)) {
            v.setInt32(WEXITSTATUS(status));
            if (!JS_DefineProperty(cx, info, "exitStatus", v, JSPROP_ENUMERATE))
                return false;
        }
    }

    args.rval().setObject(*info);
    return true;
}
#endif

static const JSFunctionSpecWithHelp os_functions[] = {
    JS_FN_HELP("getenv", os_getenv, 1, 0,
"getenv(variable)",
"  Get the value of an environment variable."),

    JS_FN_HELP("getpid", os_getpid, 0, 0,
"getpid()",
"  Return the current process id."),

    JS_FN_HELP("system", os_system, 1, 0,
"system(command)",
"  Execute command on the current host, returning result code or throwing an\n"
"  exception on failure."),

#ifndef XP_WIN
    JS_FN_HELP("spawn", os_spawn, 1, 0,
"spawn(command)",
"  Start up a separate process running the given command. Returns the pid."),

    JS_FN_HELP("kill", os_kill, 1, 0,
"kill(pid[, signal])",
"  Send a signal to the given pid. The default signal is SIGINT. The signal\n"
"  passed in must be numeric, if given."),

    JS_FN_HELP("waitpid", os_waitpid, 1, 0,
"waitpid(pid[, nohang])",
"  Calls waitpid(). 'nohang' is a boolean indicating whether to pass WNOHANG.\n"
"  The return value is an object containing a 'pid' field, if a process was waitable\n"
"  and an 'exitStatus' field if a pid exited."),
#endif

    JS_FS_HELP_END
};

bool
DefineOS(JSContext* cx, HandleObject global,
         bool fuzzingSafe,
         RCFile** shellOut, RCFile** shellErr)
{
    RootedObject obj(cx, JS_NewPlainObject(cx));
    if (!obj || !JS_DefineProperty(cx, global, "os", obj, 0))
        return false;

    if (!fuzzingSafe) {
        if (!JS_DefineFunctionsWithHelp(cx, obj, os_functions))
            return false;
    }

    RootedObject osfile(cx, JS_NewPlainObject(cx));
    if (!osfile ||
        !JS_DefineFunctionsWithHelp(cx, osfile, osfile_functions) ||
        !JS_DefineProperty(cx, obj, "file", osfile, 0))
    {
        return false;
    }

    if (!fuzzingSafe) {
        if (!JS_DefineFunctionsWithHelp(cx, osfile, osfile_unsafe_functions))
            return false;
    }

    if (!GenerateInterfaceHelp(cx, osfile, "os.file"))
        return false;

    RootedObject ospath(cx, JS_NewPlainObject(cx));
    if (!ospath ||
        !JS_DefineFunctionsWithHelp(cx, ospath, ospath_functions) ||
        !JS_DefineProperty(cx, obj, "path", ospath, 0) ||
        !GenerateInterfaceHelp(cx, ospath, "os.path"))
    {
        return false;
    }

    if (!GenerateInterfaceHelp(cx, obj, "os"))
        return false;

    gOutFilePtr = shellOut;
    gErrFilePtr = shellErr;

    // For backwards compatibility, expose various os.file.* functions as
    // direct methods on the global.
    RootedValue val(cx);

    struct {
        const char* src;
        const char* dst;
    } osfile_exports[] = {
        { "readFile", "read" },
        { "readFile", "snarf" },
        { "readRelativeToScript", "readRelativeToScript" },
        { "redirect", "redirect" },
        { "redirectErr", "redirectErr" }
    };

    for (auto pair : osfile_exports) {
        if (!JS_GetProperty(cx, osfile, pair.src, &val))
            return false;
        if (val.isObject()) {
            RootedObject function(cx, &val.toObject());
            if (!JS_DefineProperty(cx, global, pair.dst, function, 0))
                return false;
        }
    }

    return true;
}

} // namespace shell
} // namespace js