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

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< cpp‎ | io‎ | basic ostream
 
 
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(C++11)
 
 
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).

Contents

[edit] 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

[edit] Return value

*this

[edit] Exceptions

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

[edit] 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!

[edit] 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

[edit] See also

returns the output position indicator
(public member function) [edit]
returns the input position indicator
(public member function of std::basic_istream<CharT,Traits>) [edit]
sets the input position indicator
(public member function of std::basic_istream<CharT,Traits>) [edit]