mrw-cxx/mrw/exec.cpp

/** @file

    $Id$

    $Date$
    $Author$

    @copy © Marc Wäckerlin
    @license LGPL, see file <a href="license.html">COPYING</a>

    $Log$
    Revision 1.8  2004/12/18 21:00:09  marc
    everything is ok, when pipes are non blocking on parent's side and blocking on client's side, and select is not used (not necessary for non blocking IO)

    Revision 1.7  2004/12/17 17:38:57  marc
    it works perfectly with blocking pipes and buffer size of 1

    Revision 1.6  2004/12/17 16:28:51  marc
    stable implementation with select for both executes

    Revision 1.5  2004/12/14 20:30:09  marc
    added possibility to pass string to stdin of child process

    Revision 1.4  2004/08/28 16:21:25  marc
    mrw-c++-0.92 (mrw)
    - new file: version.cpp
    - new file header for all sources
    - work around warning in mrw::auto<T>
    - possibility to compile without log4cxx
    - work around bugs in demangle.h and libiberty.h
    - corrections in documentation
    - added simple tracing mechanism
    - more warnings
    - small corrections in Auto<>::Free and a new test for it
    - possibility to compile without stack trace

*/
#include <mrw/exec.hpp>
#include <mrw/unistd.hpp>
#include <mrw/exception.hpp>
#include <mrw/stdext.hpp> // max
#include <sys/wait.h> // waitpid#include <unistd.h> // fork, exec
#include <string.h> // memcpy
#include <assert.h> // assert

mrw::ExecutionFailedExc::ExecutionFailedExc(const std::string& w,
                                            const std::string& c)
  throw(std::bad_exception):
  _what(std::string("mrw::Exec: command execution failed\n")+
        std::string("           failed command was: \""+c+"\"\n")+
        std::string("           error was: \"")+w+'"') {
  /**
      @c what looks like:
      @verbatim
      mrw::Exec: command execution failed
                 failed command was: "/bin/OOOOPS -v -q --crash"
                 error was: "execution failed"
      @endverbatim
  */
}

mrw::Cmd::Cmd(const std::string& c) throw(std::bad_exception) {
  _cmd.push_back(c);
}

mrw::Cmd& mrw::Cmd::operator,(const std::string& arg)
  throw(std::bad_exception) {
  _cmd.push_back(arg);
  return *this;
}

mrw::Cmd& mrw::Cmd::operator<<(const std::string& arg)
  throw(std::bad_exception) {
  _cmd.push_back(arg);
  return *this;
}

mrw::Cmd::operator std::string() const throw(std::bad_exception) {
  ArgList::const_iterator it(_cmd.begin());
  std::string c(*it);
  while (++it!=_cmd.end()) c+=' '+*it;
  return c;
}

mrw::Cmd::operator mrw::Exec() const throw(std::bad_exception) {
  return mrw::Exec(*this);
}

mrw::Exec mrw::Cmd::execute(bool exc) const throw(std::exception) {
  return mrw::Exec(*this).execute(exc);
}

mrw::Exec mrw::Cmd::execute(const std::string& input, bool exc) const
  throw(std::exception) {
  return mrw::Exec(*this).execute(input, exc);
}

const char* mrw::Cmd::path() const throw(std::bad_exception) {
  return _cmd.front().c_str();
}
char** mrw::Cmd::args() const throw(std::bad_exception) {
  if (_cmd.size()==0) return 0;
  char** array = new char*[_cmd.size()+1];
  int i(0);
  for (ArgList::const_iterator it(_cmd.begin()); it!=_cmd.end(); ++it)
    memcpy(array[i++]=new char[it->size()+1], it->c_str(), it->size()+1);
  array[i] = 0;
  return array;
}

mrw::Exec::Exec(const mrw::Cmd& c) throw(std::bad_exception):
  _cmd(new mrw::Cmd(c)), _success(false) {
}

mrw::Exec::Exec(const mrw::Exec& e) throw(std::bad_exception):
  _cmd(new mrw::Cmd(*e._cmd)),
  _res(e._res), _err(e._err), _success(e._success) {
}

mrw::Exec::~Exec() throw() {
  delete _cmd;
}

mrw::Exec& mrw::Exec::operator=(const mrw::Exec& e) throw(std::bad_exception) {
  if (this==&e) return *this;
  *_cmd=*e._cmd; _res=e._res; _err=e._err; _success=e._success;
  return *this;
}

mrw::Exec& mrw::Exec::execute(bool exc) throw(std::exception) {
  /** This method calls @c fork, sets up a pipe connection to pass @c
      stdout and @c stderr from the child process to the parent
      process using mrw::Pipe and calls @c execvp to execute the
      program. */
  _success = false;
  _res = _err = "";
  mrw::Pipe stdOut(mrw::Pipe::block_output), stdErr(mrw::Pipe::block_output);
  if (!stdOut || !stdErr)
    throw mrw::ExecutionFailedExc("cannot create pipe", *_cmd);
  pid_t pid(fork());
  if (pid<0)
    throw ExecutionFailedExc("cannot fork", *_cmd);
  if (pid) { // parent
    stdOut.close_out();
    stdErr.close_out();
    if (!stdOut || !stdErr)
      throw ExecutionFailedExc("cannot close pipe", *_cmd);
    ssize_t num1(1), num2(1);
    char buf[4096];
    int res(0), s(0);
    /** @bug @b Solved: It sometimes did not get the whole input
             since I changed to non blocking pipes. Now I have found
             the solution to the problems: Non blocking IO does not
             work in conjunction with @c select! Also the pipe must
             not be nonblocking on both ends, but only on one. */
    while (num1||num2||!res) try { // not end of files or child terminated
      if (!res && (res=waitpid(pid, &s, WNOHANG)))
        if (res!=pid || WIFEXITED(s)!=0 && WEXITSTATUS(s)!=0)
          throw ExecutionFailedExc("execution failed", *_cmd);
      if (num1<=0&&num2<=0) usleep(10000); // nothing to read last time
      // check and handle stdout
      if (num1 && (num1=read(stdOut.istream(), buf, sizeof(buf)))>0)
        _res += std::string(buf, num1);
      else if (num1==-1 && (errno!=EINTR&&errno!=EAGAIN))
        throw ExecutionFailedExc("readin stdout", *_cmd);
      // check and handle stderr
      if (num2 && (num2=read(stdErr.istream(), buf, sizeof(buf)))>0)
        _err += std::string(buf, num2);
      else if (num2==-1 && (errno!=EINTR&&errno!=EAGAIN))
        throw ExecutionFailedExc("readin stderr", *_cmd);
    } catch (...) {
      if (exc) throw;
      _success = false;
      return *this;
    }
  } else { // child
    stdOut.close_in();
    stdErr.close_in();
    stdOut.connect_cout();
    stdErr.connect_cerr();
    execvp(_cmd->path(), _cmd->args());
    exit(1); // execute failed
  }
  _success = true;
  return *this;
}

mrw::Exec& mrw::Exec::execute(const std::string& input, bool exc)
  throw(std::exception) {
  /// @c input length must be smaller than @c SSIZE_MAX.
  /// I'll only add support for longer strings upon request.
  assert(input.size()<=SSIZE_MAX &&
         "sdin input exeeds C library limit in mrw::Exec "
         "please contact the author of the library");
  /** This method calls @c fork, sets up a pipe connection to pass @c
      stdin, @c stdout and @c stderr from the child process to the
      parent process using mrw::Pipe and calls @c execvp to execute
      the program. */
  _success = false;
  _res = _err = "";
  mrw::Pipe stdIn(mrw::Pipe::block_input),
    stdOut(mrw::Pipe::block_output), stdErr(mrw::Pipe::block_output);
  if (!stdIn || !stdOut || !stdErr)
    throw mrw::ExecutionFailedExc("cannot create pipe", *_cmd);
  pid_t pid(fork());
  if (pid<0) throw ExecutionFailedExc("cannot fork", *_cmd);
  if (pid) { // parent
    stdIn.close_in();
    stdOut.close_out();
    stdErr.close_out();
    if (!stdIn || !stdOut || !stdErr)
      throw ExecutionFailedExc("cannot close pipes", *_cmd);
    ssize_t num0(1), num1(1), num2(1);
    std::string in(input);
    char buf[4096];
    int res(0), s(0);
    /** @bug @b Solved: It sometimes did not get the whole input
             since I changed to non blocking pipes. Now I have found
             the solution to the problems: Non blocking IO does not
             work in conjunction with @c select! Also the pipe must
             not be nonblocking on both ends, but only on one. */
    while (num0||num1||num2||!res) try { // not end of files or child terminated
      if (!res && (res=waitpid(pid, &s, WNOHANG)))
        if (res!=pid || WIFEXITED(s)!=0 && WEXITSTATUS(s)!=0)
          throw ExecutionFailedExc("execution failed", *_cmd);
      if (num0<=0&&num1<=0&&num2<=0) usleep(10000); // no activity last time
      // check and handle stdin
      if (num0 && (num0=write(stdIn.ostream(), in.c_str(), in.size()))>0) {
        if ((unsigned int)num0<in.size())
          in = in.substr(num0);
        else if ((unsigned int)num0==in.size())
          num0=0, stdIn.close_out();
      } else if (num0==-1 && (errno!=EINTR&&errno!=EAGAIN))
        throw ExecutionFailedExc("writing stdin", *_cmd);
      // check and handle stdout
      if (num1 && (num1=read(stdOut.istream(), buf, sizeof(buf)))>0)
        _res += std::string(buf, num1);
      else if (num1==-1 && (errno!=EINTR&&errno!=EAGAIN))
        throw ExecutionFailedExc("readin stdout", *_cmd);
      // check and handle stderr
      if (num2 && (num2=read(stdErr.istream(), buf, sizeof(buf)))>0)
        _err += std::string(buf, num2);
      else if (num2==-1 && (errno!=EINTR&&errno!=EAGAIN))
        throw ExecutionFailedExc("readin stderr", *_cmd);
    } catch (...) {
      if (exc) throw;
      _success = false;
      return *this;
    }
  } else { // child
    stdIn.close_out();
    stdOut.close_in();
    stdErr.close_in();
    stdIn.connect_cin();
    stdOut.connect_cout(); // if cin is non blocking, child terminates here?!?
    stdErr.connect_cerr();
    execvp(_cmd->path(), _cmd->args());
    exit(1); // execute failed
  }
  _success = true;
  return *this;
}

mrw::Exec& mrw::Exec::operator>>(std::string& res) throw(std::exception) {
  execute();
  res += _res;
  return *this;
}

mrw::Exec::operator std::string&() throw(std::exception) {
  if (!_success) execute();
  return _res;
}

mrw::Exec::operator bool() throw(std::bad_exception) {
  return _success;
}

std::string& mrw::Exec::result() throw(std::exception) {
  if (!_success) execute();
  return _res;
}

std::string& mrw::Exec::error() throw(std::exception) {
  if (!_success) execute();
  return _err;
}

bool mrw::Exec::success() throw(std::bad_exception) {
  return _success;
}