std::basic_ostream<CharT,Traits>::seekp
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basic_ostream::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) if fail() != true, 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 ). In case of failure, calls setstate(std::ios_base::failbit ).
2) if fail() != true, sets the output position indicator to offset off relative to dir by calling rdbuf()->pubseekoff(off, dir, std::ios_base::out ). In case of failure, calls setstate(std::ios_base::failbit ).
[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
[edit] Example
Run this code
#include <iostream> #include <sstream> 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 129 | C++98 | there was no way to indicate a failure | sets failbit on failure
|
| LWG 136 | C++98 | seekp could set the input stream
|
only sets the output stream |
| LWG 537 | C++98 | 1. the type of pos was pos_type&2. the type of off was off_type&
|
1. corrected to pos_type2. corrected to off_type
|
| LWG 2341 | C++98 | the resolution of LWG issue 129 for overload (2) was removed | restored |
[edit] See also
returns the input position indicator
(public member function of
(public member function of
std::basic_istream<CharT,Traits>) [edit]