TRedirect.h

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#ifndef TREDIRECT_H
#define TREDIRECT_H
 
#include <cstdio>
#include <cstdlib>
#include <fcntl.h>
#include <unistd.h>
 
/////////////////////////////////////////////////////////////////
///
/// \class TRedirect
///
/// A simple class to redirect stdout and stderr to file(s). To
/// use it, create it, providing the path of the files stdout and
/// stderr should be redirected to, and an (optional) flag whether
/// to append to those files (default) or not.
/// If only one file is provided, both stdout and stderr are
/// redirected to it.
/// If the filename for either stdout or stderr is a nullptr, the
/// redirection for this output won't happen.
/// The redirection ends when the TRedirect object is destroyed.
///
/////////////////////////////////////////////////////////////////
 
class TRedirect {
public:
   TRedirect(const char* newOut, const char* newErr, bool append = true)
      : fOutFile(newOut), fErrFile(newErr)
   {
      Redirect(append);
   }
   explicit TRedirect(const char* newOut, bool append = true)
      : fOutFile(newOut), fErrFile(newOut)
   {
      Redirect(append);
   }
 
   const char* OutFile() { return fOutFile; }
   const char* ErrFile() { return fErrFile; }
 
   ~TRedirect()
   {
      fflush(stdout);
      dup2(fStdOutFileDescriptor, fileno(stdout));
      close(fStdOutFileDescriptor);
      fflush(stderr);
      dup2(fStdErrFileDescriptor, fileno(stderr));
      close(fStdErrFileDescriptor);
   }
 
   TRedirect(const TRedirect&) = delete;
   TRedirect(TRedirect&&)      = delete;
 
   TRedirect& operator=(const TRedirect&) = delete;
   TRedirect& operator=(TRedirect&&)      = delete;
 
private:
   void Redirect(bool append)
   {
      if(fOutFile != nullptr) {
         fStdOutFileDescriptor = dup(fileno(stdout));
         fflush(stdout);
         int newStdOut = open(fOutFile, (append ? O_WRONLY | O_CREAT | O_APPEND : O_WRONLY | O_CREAT), S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH);
         dup2(newStdOut, fileno(stdout));
         close(newStdOut);
      }
      if(fErrFile != nullptr) {
         fStdErrFileDescriptor = dup(fileno(stderr));
         fflush(stderr);
         int newStdErr = open(fErrFile, (append ? O_WRONLY | O_CREAT | O_APPEND : O_WRONLY | O_CREAT), S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH);
         dup2(newStdErr, fileno(stderr));
         close(newStdErr);
      }
   }
 
   int         fStdOutFileDescriptor{0};
   int         fStdErrFileDescriptor{0};
   const char* fOutFile{nullptr};
   const char* fErrFile{nullptr};
};
 
#endif