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Defined in header
template<classCharT,classTraits>basic_istream<CharT,Traits>&operator>>(basic_istream<CharT,Traits>&st,CharT&ch);template<classTraits>basic_istream<char,Traits>&operator>>(basic_istream<char,Traits>&st,signedchar&ch);template<classTraits>basic_istream<char,Traits>&operator>>(basic_istream<char,Traits>&st,unsignedchar&ch); (1) template<classCharT,classTraits>basic_istream<CharT,Traits>&operator>>(basic_istream<CharT,Traits>&st,CharT*s);template<classTraits>basic_istream<char,Traits>&operator>>(basic_istream<char,Traits>&st,signedchar*s);template<classTraits>basic_istream<char,Traits>&operator>>(basic_istream<char,Traits>&st,unsignedchar*s); (2)(until C++20)template<classCharT,classTraits,std::size_tN>basic_istream<CharT,Traits>&operator>>(basic_istream<CharT,Traits>&st,CharT(&s)[N]);template<classTraits,std::size_tN>basic_istream<char,Traits>&operator>>(basic_istream<char,Traits>&st,signedchar(&s)[N]);template<classTraits,std::size_tN>basic_istream<char,Traits>&operator>>(basic_istream<char,Traits>&st,unsignedchar(&s)[N]);(since C++20)template<classIstream,classT>Istream&&operator>>(Istream&&st,T&&value); (3) (since C++11)1,2) Performs character input operations.
1) Behaves as a
. After constructing and checking the sentry object, which may skip leading whitespace, extracts a character and stores it to ch. If no character is available, sets
(in addition to
that is set as required of a
).
2) Behaves as a
. After constructing and checking the sentry object, which may skip leading whitespace, extracts successive characters and stores them at successive locations of a character array whose first element is pointed to by(until C++20)s. The extraction stops if any of the following conditions is met:
A whitespace character (as determined by the
facet) is found. The whitespace character is not extracted.
If st.width() is greater than zero, st.width()-1 characters are stored.
(until C++20)n-1 characters are stored, where n is defined as follows:
If st.width() is greater than zero, std::min(std::size_t(st.width()),N);
otherwise, n is N.
(since C++20)End of file occurs in the input sequence (this also sets
).
In either case, an additional null character value CharT() is stored at the end of the output. If no characters were extracted, sets
(the null character is still written, to the first position in the output). Finally, calls st.width(0) to cancel the effects of
, if any.
3) Calls the appropriate extraction operator, given an rvalue reference to an input stream object (equivalent to st>>std::forward<T>(value)). This overload participates in overload resolution only if st>>std::forward<T>(value) is well-formed and Istream is a class type publicly and unambiguously derived from
.
Notes
Extracting a single character that is the last character of the stream does not set eofbit: this is different from other formatted input functions, such as extracting the last integer with operator>>, but this behavior matches the behavior of
with "%c" format specifier.
Parameters
st - input stream to extract the data from ch - reference to a character to store the extracted character to s - pointer to(until C++20) a character array to store the extracted characters to Return value
1,2)st
3)std::move(st)
Example
Run this code
#include<iomanip>#include<iostream>#include<sstream>intmain(){std::stringinput="n greetings";std::istringstreamstream(input);charc;constintMAX=6;charcstr[MAX];stream>>c>>std::setw(MAX)>>cstr;std::cout<<"c = "<<c<<'\n'<<"cstr = "<<cstr<<'\n';doublef;std::istringstream("1.23")>>f;// rvalue stream extractionstd::cout<<"f = "<<f<<'\n';}Output:
c = n cstr = greet f = 1.23 Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
DR Applied to Behavior as published Correct behavior
C++98 the definition of n mentioned a non-existing name eosreplaced with CharT()
C++98 no null characters were stored at the end of the output for overload (2) stores a null character
C++98 overload for rvalue stream returned lvalue reference to the base class returns rvalue reference
to the derived class
C++98 overload for rvalue stream required another argument to be lvalue made to accept rvalue
C++98 overload for rvalue stream was not constrained constrained See also