std::basic_ostream<CharT,Traits>::seekp (3) - Linux Manuals

std::basic_ostream<CharT,Traits>::seekp: std::basic_ostream<CharT,Traits>::seekp

NAME

std::basic_ostream<CharT,Traits>::seekp - std::basic_ostream<CharT,Traits>::seekp

Synopsis

basic_ostream& seekp( pos_type pos ); (1)
basic_ostream& seekp( off_type off, std::ios_base::seekdir dir ); (2)

Sets the output position indicator of the current associated streambuf object.

Behaves as UnformattedOutputFunction (except without actually performing output). After constructing and checking the sentry object, (since C++11)

1) sets the output position indicator to absolute (relative to the beginning of the file) value pos by calling rdbuf()->pubseekpos(pos, std::ios_base::out). If the call returns (pos_type)-1, executes setstate(failbit).
2) sets the output position indicator to offset off relative to dir by calling rdbuf()->pubseekoff(off, dir, std::ios_base::out).

Does not report errors. (until C++14)
If the call returns (pos_type)-1, executes setstate(failbit). (since C++14)

Parameters

pos - absolute position to set the output position indicator to.
off - relative position to set the output position indicator to.
      defines base position to apply the relative offset to. It can be one of the following constants:

      Constant Explanation
dir - beg the beginning of a stream
      end the ending of a stream
      cur the current position of stream position indicator

Return value

*this

Exceptions

1) May throw std::ios_base::failure in case of failure, if exceptions() & failbit != 0.
2)

Does not throw unless rdbuf()->pubseekoff() throws (until C++14)
May throw std::ios_base::failure in case of failure, if exceptions() & failbit != 0. (since C++14)

Example

// Run this code

  #include <sstream>
  #include <iostream>

  int main()
  {
      std::ostringstream os("hello, world");
      os.seekp(7);
      os << 'W';
      os.seekp(0, std::ios_base::end);
      os << '!';
      os.seekp(0);
      os << 'H';
      std::cout << os.str() << '\n';
  }

Output:

  Hello, World!