std::basic_ostream::seekp

 

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Technical Specifications

 

Input/output library

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basic_streambuf

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basic_osyncstream (C++20)

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streamoff

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std::basic_ostream

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coutwcout	cerrwcerr	clogwclog
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basic_ostream::basic_ostream
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basic_ostream::tellp
basic_ostream::seekp
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basic_ostream::sentry
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operator<<(std::basic_ostream)

 

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

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!

See also

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