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

 

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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). If the call returns (pos_type)-1, executes setstate(failbit).

Parameters

pos	-	absolute position to set the output position indicator to.
off	-	relative position (positive or negative) to set the output position indicator to.
dir	-	defines base position to apply the relative offset to. It can be one of the following constants: Constant Explanation beg the beginning of a stream end the ending of a stream cur the current position of stream position indicator

Return value

*this

Exceptions

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

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!

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR	Applied to	Behavior as published	Correct behavior
LWG 2341	C++98	two overloads behaved differently on failure	made consistent

See also

tellp	returns the output position indicator (public member function)
tellg	returns the input position indicator (public member function of std::basic_istream<CharT,Traits>)
seekg	sets the input position indicator (public member function of std::basic_istream<CharT,Traits>)