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std::basic_ostream::seekp

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.
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) 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

#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!

See also

returns the output position indicator
(public member function)
returns the input position indicator
(public member function of std::basic_istream)
sets the input position indicator
(public member function of std::basic_istream)

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