std::basic_istream::peek

 

C++

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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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std::basic_istream

Global objects

cinwcin

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basic_istream::basic_istream

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basic_istream::operator= (C++11)

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basic_istream::operator>>

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basic_istream::get

basic_istream::peek

basic_istream::unget

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basic_istream::getline

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basic_istream::readsome

basic_istream::gcount

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basic_istream::tellg

basic_istream::seekg

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basic_istream::sync

basic_istream::swap (C++11)

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basic_istream::sentry

Non-member functions

operator>>(std::basic_istream)

 

int_type peek();

Behaves as UnformattedInputFunction. After constructing and testing the sentry object, reads the next character from the input stream without extracting it.

Parameters

(none)

Return value

If good() == true, returns the next character as obtained by rdbuf()->sgetc()

Otherwise, returns Traits::eof().

Exceptions

failure if an error occurred (the error state flag is not goodbit) and exceptions() is set to throw for that state.

If an internal operation throws an exception, it is caught and badbit is set. If exceptions() is set for badbit, the exception is rethrown.

Example

Run this code

#include <sstream>
#include <iostream>
int main()
{
    std::istringstream s1("Hello, world.");
    char c1 = s1.peek();
    char c2 = s1.get();
    std::cout << "Peeked: " << c1 << " got: " << c2 << '\n';
}

Output:

Peeked: H got: H

See also

sgetc	reads one character from the input sequence without advancing the sequence (public member function of std::basic_streambuf)
get	extracts characters (public member function)
unget	unextracts a character (public member function)