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

From cppreference.com

Compiler support
Freestanding and hosted
Language
Standard library
Standard library headers
Named requirements
Feature test macros(C++20)
Language support library
Concepts library(C++20)
Diagnostics library
Memory management library
Metaprogramming library(C++11)
General utilities library
Containers library
Iterators library
Ranges library(C++20)
Algorithms library
Strings library
Text processing library
Numerics library
Date and time library
Input/output library
Filesystem library(C++17)
Concurrency support library(C++11)
Execution control library(C++26)
Technical specifications
Symbols index
External libraries

[edit]

Input/output library

I/O manipulators
Print functions(C++23)
C-style I/O
Buffers
basic_streambuf
basic_filebuf
basic_stringbuf
basic_spanbuf (C++23)
strstreambuf (C++98/26*)
basic_syncbuf (C++20)
Streams
Abstractions
ios_base
basic_ios
basic_istream
basic_ostream
basic_iostream
File I/O
basic_ifstream
basic_ofstream
basic_fstream
String I/O
basic_istringstream
basic_ostringstream
basic_stringstream
Array I/O
basic_ispanstream (C++23)
basic_ospanstream (C++23)
basic_spanstream (C++23)
istrstream (C++98/26*)
ostrstream (C++98/26*)
strstream (C++98/26*)
Synchronized Output
basic_osyncstream (C++20)
Types
streamoff
streamsize
fpos
Error category interface
iostream_category (C++11)
io_errc (C++11)

Global objects

Member functions

basic_ostream::basic_ostream

basic_ostream::~basic_ostream

basic_ostream::operator=

(C++11)

Formatted output

basic_ostream::operator<<

Unformatted output

basic_ostream::put

basic_ostream::write

Positioning

basic_ostream::tellp

basic_ostream::seekp

Miscellaneous

basic_ostream::flush

basic_ostream::swap

(C++11)

Member classes

basic_ostream::sentry

Non-member functions

operator<<(std::basic_ostream)

print(std::ostream)

(C++23)

println(std::ostream)

(C++23)

vprint_unicode(std::ostream)

(C++23)

vprint_nonunicode(std::ostream)

(C++23)

[edit]

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 associatedstreambuf object.

Behaves asUnformattedOutputFunction (except without actually performing output). After constructing and checking the sentry object,

(since C++11)

1) iffail()!=true, sets the output position indicator to absolute (relative to the beginning of the file) valuepos by callingrdbuf()->pubseekpos(pos,std::ios_base::out). In case of failure, callssetstate(std::ios_base::failbit).

2) iffail()!=true, sets the output position indicator to offsetoff relative todir by callingrdbuf()->pubseekoff(off, dir,std::ios_base::out). In case of failure, callssetstate(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

1,2) May throwstd::ios_base::failure in case of failure, ifexceptions()& failbit!=0.

[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 ofpos was`pos_type&` 2. the type ofoff was`off_type&`	1. corrected to`pos_type` 2. corrected to`off_type`
LWG 2341	C++98	the resolution ofLWG issue 129 for overload (2) was removed	restored

[edit]See also

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