std::basic_ostream<CharT,Traits>:: seekp
From cppreference.com
<
cpp
|
io
|
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)
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
)
.
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:
|
Return value
* this
Exceptions
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!
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_type
2. corrected to
off_type
|
| LWG 2341 | C++98 | the resolution of LWG issue 129 for overload (2) was removed | restored |
See also
|
returns the output position indicator
(public member function) |
|
|
returns the input position indicator
(public member function of
std::basic_istream<CharT,Traits>
)
|
|
|
sets the input position indicator
(public member function of
std::basic_istream<CharT,Traits>
)
|