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// Copyright 2009 the V8 project authors. All rights reserved.
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// Redistribution and use in source and binary forms, with or without
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// modification, are permitted provided that the following conditions are
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// * Redistributions of source code must retain the above copyright
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// notice, this list of conditions and the following disclaimer.
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// * Redistributions in binary form must reproduce the above
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// copyright notice, this list of conditions and the following
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// disclaimer in the documentation and/or other materials provided
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// with the distribution.
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// * Neither the name of Google Inc. nor the names of its
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// contributors may be used to endorse or promote products derived
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// from this software without specific prior written permission.
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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#include <sys/types.h>
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// If the buffer ends in the middle of a UTF-8 sequence then we return
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// the length of the string up to but not including the incomplete UTF-8
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// sequence. If the buffer ends with a valid UTF-8 sequence then we
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// return the whole buffer.
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static int LengthWithoutIncompleteUtf8(char* buffer, int len) {
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static const int kUtf8SingleByteMask = 0x80;
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static const int kUtf8SingleByteValue = 0x00;
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static const int kUtf8TwoByteMask = 0xe0;
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static const int kUtf8TwoByteValue = 0xc0;
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static const int kUtf8ThreeByteMask = 0xf0;
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static const int kUtf8ThreeByteValue = 0xe0;
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static const int kUtf8FourByteMask = 0xf8;
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static const int kUtf8FourByteValue = 0xf0;
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// Subsequent bytes of a multi-byte encoding.
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static const int kMultiByteMask = 0xc0;
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static const int kMultiByteValue = 0x80;
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int multi_byte_bytes_seen = 0;
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int c = buffer[answer - 1];
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// Ends in valid single-byte sequence?
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if ((c & kUtf8SingleByteMask) == kUtf8SingleByteValue) return answer;
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// Ends in one or more subsequent bytes of a multi-byte value?
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if ((c & kMultiByteMask) == kMultiByteValue) {
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multi_byte_bytes_seen++;
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if ((c & kUtf8TwoByteMask) == kUtf8TwoByteValue) {
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if (multi_byte_bytes_seen >= 1) {
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} else if ((c & kUtf8ThreeByteMask) == kUtf8ThreeByteValue) {
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if (multi_byte_bytes_seen >= 2) {
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} else if ((c & kUtf8FourByteMask) == kUtf8FourByteValue) {
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if (multi_byte_bytes_seen >= 3) {
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return answer; // Malformed UTF-8.
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// Suspends the thread until there is data available from the child process.
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// Returns false on timeout, true on data ready.
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static bool WaitOnFD(int fd,
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struct timeval& start_time) {
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fd_set readfds, writefds, exceptfds;
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struct timeval timeout;
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if (total_timeout != -1) {
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struct timeval time_now;
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gettimeofday(&time_now, NULL);
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int seconds = time_now.tv_sec - start_time.tv_sec;
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gone = seconds * 1000 + (time_now.tv_usec - start_time.tv_usec) / 1000;
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if (gone >= total_timeout) return false;
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FD_SET(fd, &readfds);
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FD_SET(fd, &exceptfds);
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if (read_timeout == -1 ||
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(total_timeout != -1 && total_timeout - gone < read_timeout)) {
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read_timeout = total_timeout - gone;
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timeout.tv_usec = (read_timeout % 1000) * 1000;
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timeout.tv_sec = read_timeout / 1000;
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int number_of_fds_ready = select(fd + 1,
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read_timeout != -1 ? &timeout : NULL);
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return number_of_fds_ready == 1;
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// Checks whether we ran out of time on the timeout. Returns true if we ran out
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// of time, false if we still have time.
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static bool TimeIsOut(const struct timeval& start_time, const int& total_time) {
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if (total_time == -1) return false;
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struct timeval time_now;
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gettimeofday(&time_now, NULL);
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// Careful about overflow.
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int seconds = time_now.tv_sec - start_time.tv_sec;
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if (seconds * 1000 > total_time) return true;
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int useconds = time_now.tv_usec - start_time.tv_usec;
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if (seconds * 1000000 + useconds > total_time * 1000) {
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// A utility class that does a non-hanging waitpid on the child process if we
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// bail out of the System() function early. If you don't ever do a waitpid on
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// a subprocess then it turns into one of those annoying 'zombie processes'.
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class ZombieProtector {
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explicit ZombieProtector(int pid): pid_(pid) { }
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~ZombieProtector() { if (pid_ != 0) waitpid(pid_, NULL, 0); }
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void ChildIsDeadNow() { pid_ = 0; }
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// A utility class that closes a file descriptor when it goes out of scope.
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explicit OpenFDCloser(int fd): fd_(fd) { }
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~OpenFDCloser() { close(fd_); }
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// A utility class that takes the array of command arguments and puts then in an
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// array of new[]ed UTF-8 C strings. Deallocates them again when it goes out of
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exec_args_[0] = NULL;
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bool Init(Handle<Value> arg0, Handle<Array> command_args) {
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String::Utf8Value prog(arg0);
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const char* message =
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"os.system(): String conversion of program name failed";
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ThrowException(String::New(message));
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int len = prog.length() + 3;
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char* c_arg = new char[len];
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snprintf(c_arg, len, "%s", *prog);
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exec_args_[0] = c_arg;
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for (unsigned j = 0; j < command_args->Length(); i++, j++) {
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Handle<Value> arg(command_args->Get(Integer::New(j)));
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String::Utf8Value utf8_arg(arg);
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if (*utf8_arg == NULL) {
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exec_args_[i] = NULL; // Consistent state for destructor.
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const char* message =
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"os.system(): String conversion of argument failed.";
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ThrowException(String::New(message));
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int len = utf8_arg.length() + 1;
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char* c_arg = new char[len];
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snprintf(c_arg, len, "%s", *utf8_arg);
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exec_args_[i] = c_arg;
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exec_args_[i] = NULL;
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for (unsigned i = 0; i < kMaxArgs; i++) {
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if (exec_args_[i] == NULL) {
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delete [] exec_args_[i];
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static const unsigned kMaxArgs = 1000;
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char** arg_array() { return exec_args_; }
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char* arg0() { return exec_args_[0]; }
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char* exec_args_[kMaxArgs + 1];
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// Gets the optional timeouts from the arguments to the system() call.
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static bool GetTimeouts(const Arguments& args,
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int* total_timeout) {
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if (args.Length() > 3) {
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if (args[3]->IsNumber()) {
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*total_timeout = args[3]->Int32Value();
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ThrowException(String::New("system: Argument 4 must be a number"));
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if (args.Length() > 2) {
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if (args[2]->IsNumber()) {
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*read_timeout = args[2]->Int32Value();
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ThrowException(String::New("system: Argument 3 must be a number"));
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static const int kReadFD = 0;
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static const int kWriteFD = 1;
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// This is run in the child process after fork() but before exec(). It normally
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// ends with the child process being replaced with the desired child program.
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// It only returns if an error occurred.
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static void ExecSubprocess(int* exec_error_fds,
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ExecArgs& exec_args) {
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close(exec_error_fds[kReadFD]); // Don't need this in the child.
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close(stdout_fds[kReadFD]); // Don't need this in the child.
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close(1); // Close stdout.
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dup2(stdout_fds[kWriteFD], 1); // Dup pipe fd to stdout.
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close(stdout_fds[kWriteFD]); // Don't need the original fd now.
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fcntl(exec_error_fds[kWriteFD], F_SETFD, FD_CLOEXEC);
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execvp(exec_args.arg0(), exec_args.arg_array());
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// Only get here if the exec failed. Write errno to the parent to tell
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// them it went wrong. If it went well the pipe is closed.
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bytes_written = write(exec_error_fds[kWriteFD], &err, sizeof(err));
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} while (bytes_written == -1 && errno == EINTR);
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// Return (and exit child process).
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// Runs in the parent process. Checks that the child was able to exec (closing
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// the file desriptor), or reports an error if it failed.
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static bool ChildLaunchedOK(int* exec_error_fds) {
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bytes_read = read(exec_error_fds[kReadFD], &err, sizeof(err));
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} while (bytes_read == -1 && errno == EINTR);
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if (bytes_read != 0) {
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ThrowException(String::New(strerror(err)));
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// Accumulates the output from the child in a string handle. Returns true if it
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// succeeded or false if an exception was thrown.
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static Handle<Value> GetStdout(int child_fd,
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struct timeval& start_time,
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Handle<String> accumulator = String::Empty();
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static const int kStdoutReadBufferSize = 4096;
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char buffer[kStdoutReadBufferSize];
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if (fcntl(child_fd, F_SETFL, O_NONBLOCK) != 0) {
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return ThrowException(String::New(strerror(errno)));
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bytes_read = read(child_fd,
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kStdoutReadBufferSize - fullness);
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if (bytes_read == -1) {
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if (errno == EAGAIN) {
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if (!WaitOnFD(child_fd,
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(TimeIsOut(start_time, total_timeout))) {
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return ThrowException(String::New("Timed out waiting for output"));
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} else if (errno == EINTR) {
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if (bytes_read + fullness > 0) {
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int length = bytes_read == 0 ?
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bytes_read + fullness :
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LengthWithoutIncompleteUtf8(buffer, bytes_read + fullness);
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Handle<String> addition = String::New(buffer, length);
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accumulator = String::Concat(accumulator, addition);
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fullness = bytes_read + fullness - length;
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memcpy(buffer, buffer + length, fullness);
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} while (bytes_read != 0);
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// Modern Linux has the waitid call, which is like waitpid, but more useful
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// if you want a timeout. If we don't have waitid we can't limit the time
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// waiting for the process to exit without losing the information about
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// whether it exited normally. In the common case this doesn't matter because
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// we don't get here before the child has closed stdout and most programs don't
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// do that before they exit.
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// We're disabling usage of waitid in Mac OS X because it doens't work for us:
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// a parent process hangs on waiting while a child process is already a zombie.
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// See http://code.google.com/p/v8/issues/detail?id=401.
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#if defined(WNOWAIT) && !defined(ANDROID) && !defined(__APPLE__) \
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&& !defined(__NetBSD__)
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#if !defined(__FreeBSD__)
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// Get exit status of child.
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static bool WaitForChild(int pid,
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ZombieProtector& child_waiter,
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struct timeval& start_time,
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siginfo_t child_info;
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child_info.si_pid = 0;
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// Wait for child to exit.
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while (child_info.si_pid == 0) {
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waitid(P_PID, pid, &child_info, WEXITED | WNOHANG | WNOWAIT);
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if (useconds < 1000000) useconds <<= 1;
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if ((read_timeout != -1 && useconds / 1000 > read_timeout) ||
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(TimeIsOut(start_time, total_timeout))) {
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ThrowException(String::New("Timed out waiting for process to terminate"));
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if (child_info.si_code == CLD_KILLED) {
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"Child killed by signal %d",
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child_info.si_status);
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ThrowException(String::New(message));
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if (child_info.si_code == CLD_EXITED && child_info.si_status != 0) {
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"Child exited with status %d",
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child_info.si_status);
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ThrowException(String::New(message));
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#else // No waitid call.
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waitpid(pid, &child_status, 0); // We hang here if the child doesn't exit.
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child_waiter.ChildIsDeadNow();
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if (WIFSIGNALED(child_status)) {
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"Child killed by signal %d",
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WTERMSIG(child_status));
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ThrowException(String::New(message));
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if (WEXITSTATUS(child_status) != 0) {
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int exit_status = WEXITSTATUS(child_status);
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"Child exited with status %d",
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ThrowException(String::New(message));
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#endif // No waitid call.
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// Implementation of the system() function (see d8.h for details).
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Handle<Value> Shell::System(const Arguments& args) {
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int read_timeout = -1;
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int total_timeout = -1;
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if (!GetTimeouts(args, &read_timeout, &total_timeout)) return v8::Undefined();
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Handle<Array> command_args;
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if (args.Length() > 1) {
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if (!args[1]->IsArray()) {
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return ThrowException(String::New("system: Argument 2 must be an array"));
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command_args = Handle<Array>::Cast(args[1]);
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command_args = Array::New(0);
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if (command_args->Length() > ExecArgs::kMaxArgs) {
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return ThrowException(String::New("Too many arguments to system()"));
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if (args.Length() < 1) {
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return ThrowException(String::New("Too few arguments to system()"));
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struct timeval start_time;
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gettimeofday(&start_time, NULL);
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if (!exec_args.Init(args[0], command_args)) {
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return v8::Undefined();
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int exec_error_fds[2];
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if (pipe(exec_error_fds) != 0) {
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return ThrowException(String::New("pipe syscall failed."));
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if (pipe(stdout_fds) != 0) {
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return ThrowException(String::New("pipe syscall failed."));
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if (pid == 0) { // Child process.
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ExecSubprocess(exec_error_fds, stdout_fds, exec_args);
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// Parent process. Ensure that we clean up if we exit this function early.
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ZombieProtector child_waiter(pid);
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close(exec_error_fds[kWriteFD]);
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close(stdout_fds[kWriteFD]);
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OpenFDCloser error_read_closer(exec_error_fds[kReadFD]);
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OpenFDCloser stdout_read_closer(stdout_fds[kReadFD]);
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if (!ChildLaunchedOK(exec_error_fds)) return v8::Undefined();
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Handle<Value> accumulator = GetStdout(stdout_fds[kReadFD],
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if (accumulator->IsUndefined()) {
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kill(pid, SIGINT); // On timeout, kill the subprocess.
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if (!WaitForChild(pid,
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return v8::Undefined();
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return scope.Close(accumulator);
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Handle<Value> Shell::ChangeDirectory(const Arguments& args) {
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if (args.Length() != 1) {
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const char* message = "chdir() takes one argument";
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return ThrowException(String::New(message));
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String::Utf8Value directory(args[0]);
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if (*directory == NULL) {
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const char* message = "os.chdir(): String conversion of argument failed.";
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return ThrowException(String::New(message));
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if (chdir(*directory) != 0) {
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return ThrowException(String::New(strerror(errno)));
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return v8::Undefined();
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Handle<Value> Shell::SetUMask(const Arguments& args) {
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if (args.Length() != 1) {
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const char* message = "umask() takes one argument";
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return ThrowException(String::New(message));
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if (args[0]->IsNumber()) {
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mode_t mask = args[0]->Int32Value();
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int previous = umask(mask);
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return Number::New(previous);
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const char* message = "umask() argument must be numeric";
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return ThrowException(String::New(message));
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static bool CheckItsADirectory(char* directory) {
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struct stat stat_buf;
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int stat_result = stat(directory, &stat_buf);
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if (stat_result != 0) {
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ThrowException(String::New(strerror(errno)));
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if ((stat_buf.st_mode & S_IFDIR) != 0) return true;
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ThrowException(String::New(strerror(EEXIST)));
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// Returns true for success. Creates intermediate directories as needed. No
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// error if the directory exists already.
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static bool mkdirp(char* directory, mode_t mask) {
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int result = mkdir(directory, mask);
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if (result == 0) return true;
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if (errno == EEXIST) {
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return CheckItsADirectory(directory);
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} else if (errno == ENOENT) { // Intermediate path element is missing.
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char* last_slash = strrchr(directory, '/');
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if (last_slash == NULL) {
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ThrowException(String::New(strerror(errno)));
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if (!mkdirp(directory, mask)) return false;
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result = mkdir(directory, mask);
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if (result == 0) return true;
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if (errno == EEXIST) {
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return CheckItsADirectory(directory);
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ThrowException(String::New(strerror(errno)));
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ThrowException(String::New(strerror(errno)));
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Handle<Value> Shell::MakeDirectory(const Arguments& args) {
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if (args.Length() == 2) {
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if (args[1]->IsNumber()) {
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mask = args[1]->Int32Value();
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const char* message = "mkdirp() second argument must be numeric";
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return ThrowException(String::New(message));
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} else if (args.Length() != 1) {
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const char* message = "mkdirp() takes one or two arguments";
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return ThrowException(String::New(message));
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String::Utf8Value directory(args[0]);
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if (*directory == NULL) {
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const char* message = "os.mkdirp(): String conversion of argument failed.";
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return ThrowException(String::New(message));
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mkdirp(*directory, mask);
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return v8::Undefined();
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Handle<Value> Shell::RemoveDirectory(const Arguments& args) {
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if (args.Length() != 1) {
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const char* message = "rmdir() takes one or two arguments";
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return ThrowException(String::New(message));
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String::Utf8Value directory(args[0]);
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if (*directory == NULL) {
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const char* message = "os.rmdir(): String conversion of argument failed.";
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return ThrowException(String::New(message));
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return v8::Undefined();
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Handle<Value> Shell::SetEnvironment(const Arguments& args) {
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if (args.Length() != 2) {
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const char* message = "setenv() takes two arguments";
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return ThrowException(String::New(message));
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String::Utf8Value var(args[0]);
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String::Utf8Value value(args[1]);
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const char* message =
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"os.setenv(): String conversion of variable name failed.";
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return ThrowException(String::New(message));
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if (*value == NULL) {
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const char* message =
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"os.setenv(): String conversion of variable contents failed.";
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return ThrowException(String::New(message));
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setenv(*var, *value, 1);
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return v8::Undefined();
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Handle<Value> Shell::UnsetEnvironment(const Arguments& args) {
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if (args.Length() != 1) {
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const char* message = "unsetenv() takes one argument";
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return ThrowException(String::New(message));
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String::Utf8Value var(args[0]);
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const char* message =
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"os.setenv(): String conversion of variable name failed.";
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return ThrowException(String::New(message));
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return v8::Undefined();
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void Shell::AddOSMethods(Handle<ObjectTemplate> os_templ) {
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os_templ->Set(String::New("system"), FunctionTemplate::New(System));
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os_templ->Set(String::New("chdir"), FunctionTemplate::New(ChangeDirectory));
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os_templ->Set(String::New("setenv"), FunctionTemplate::New(SetEnvironment));
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os_templ->Set(String::New("unsetenv"),
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FunctionTemplate::New(UnsetEnvironment));
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os_templ->Set(String::New("umask"), FunctionTemplate::New(SetUMask));
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os_templ->Set(String::New("mkdirp"), FunctionTemplate::New(MakeDirectory));
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os_templ->Set(String::New("rmdir"), FunctionTemplate::New(RemoveDirectory));