exists.hpp

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// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//  http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#ifndef __STOUT_OS_POSIX_EXISTS_HPP__
#define __STOUT_OS_POSIX_EXISTS_HPP__

#include <errno.h>
#include <signal.h>

#include <sys/stat.h>

#include <string>

namespace os {


inline bool exists(const std::string& path)
{
  struct stat s;

  if (::lstat(path.c_str(), &s) < 0) {
    return false;
  }
  return true;
}


// Determine if the process identified by pid exists.
// NOTE: Zombie processes have a pid and therefore exist. See os::process(pid)
// to get details of a process.
inline bool exists(pid_t pid)
{
  // The special signal 0 is used to check if the process exists; see kill(2).
  // If the current user does not have permission to signal pid, but it does
  // exist, then ::kill will return -1 and set errno == EPERM.
  if (::kill(pid, 0) == 0 || errno == EPERM) {
    return true;
  }

  return false;
}


} // namespace os {

#endif // __STOUT_OS_POSIX_EXISTS_HPP__