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      std::basic_istream

      From cppreference.com
      <cpp‎ |io
       
       
       
       
      Defined in header<istream>
      template<

         class CharT,
         class Traits=std::char_traits<CharT>

      >class basic_istream:virtualpublicstd::basic_ios<CharT, Traits>

      The class templatebasic_istream provides support for high level input operations on character streams. The supported operations include formatted input (e.g. integer values or whitespace-separated characters and characters strings) and unformatted input (e.g. raw characters and character arrays). This functionality is implemented in terms of the interface provided by the underlyingbasic_streambuf class, accessed through thebasic_ios base class. The only non-inherited data member ofbasic_istream, in most implementations, is the value returned bybasic_istream::gcount().

      std-basic istream-inheritance.svg

      Several typedefs for common character types are provided:

      Defined in header<istream>
      Type Definition
      std::istreamstd::basic_istream<char>
      std::wistreamstd::basic_istream<wchar_t>

      Contents

      [edit]Global objects

      Two global basic_istream objects are provided by the standard library.

      Defined in header<iostream>
      reads from the standard C input streamstdin
      (global object)[edit]

      [edit]Member types

      Member type Definition
      char_typeCharT[edit]
      traits_typeTraits; the program is ill-formed ifTraits::char_type is notCharT.[edit]
      int_typeTraits::int_type[edit]
      pos_typeTraits::pos_type[edit]
      off_typeTraits::off_type[edit]

      [edit]Member functions

      constructs the object
      (public member function)[edit]
      [virtual]
      		 destructs the object
      (virtual public member function)[edit]
      (C++11)
      		 move-assigns from anotherbasic_istream
      (protected member function)[edit]
      Formatted input
      extracts formatted data
      (public member function)[edit]
      Unformatted input
      extracts characters
      (public member function)[edit]
      reads the next character without extracting it
      (public member function)[edit]
      unextracts a character
      (public member function)[edit]
      puts a character into input stream
      (public member function)[edit]
      extracts characters until the given character is found
      (public member function)[edit]
      extracts and discards characters until the given character is found
      (public member function)[edit]
      extracts blocks of characters
      (public member function)[edit]
      extracts already available blocks of characters
      (public member function)[edit]
      returns number of characters extracted by last unformatted input operation
      (public member function)[edit]
      Positioning
      returns the input position indicator
      (public member function)[edit]
      sets the input position indicator
      (public member function)[edit]
      Miscellaneous
      synchronizes with the underlying storage device
      (public member function)[edit]
      (C++11)
      		 swaps stream objects, except for the associated buffer
      (protected member function)[edit]

      [edit]Member classes

      implements basic logic for preparation of the stream for input operations
      (public member class)[edit]

      [edit]Non-member functions

      extracts characters and character arrays
      (function template)[edit]

      Inherited fromstd::basic_ios

      Member types

      Member type Definition
      char_typeCharT
      traits_typeTraits
      int_typeTraits::int_type
      pos_typeTraits::pos_type
      off_typeTraits::off_type

      Member functions

      State functions
      checks if no error has occurred i.e. I/O operations are available
      (public member function ofstd::basic_ios<CharT,Traits>)[edit]
      checks if end-of-file has been reached
      (public member function ofstd::basic_ios<CharT,Traits>)[edit]
      checks if an error has occurred
      (public member function ofstd::basic_ios<CharT,Traits>)[edit]
      checks if a non-recoverable error has occurred
      (public member function ofstd::basic_ios<CharT,Traits>)[edit]
      checks if an error has occurred (synonym offail())
      (public member function ofstd::basic_ios<CharT,Traits>)[edit]
      checks if no error has occurred (synonym of!fail())
      (public member function ofstd::basic_ios<CharT,Traits>)[edit]
      returns state flags
      (public member function ofstd::basic_ios<CharT,Traits>)[edit]
      sets state flags
      (public member function ofstd::basic_ios<CharT,Traits>)[edit]
      modifies state flags
      (public member function ofstd::basic_ios<CharT,Traits>)[edit]
      Formatting
      copies formatting information
      (public member function ofstd::basic_ios<CharT,Traits>)[edit]
      manages the fill character
      (public member function ofstd::basic_ios<CharT,Traits>)[edit]
      Miscellaneous
      manages exception mask
      (public member function ofstd::basic_ios<CharT,Traits>)[edit]
      sets the locale
      (public member function ofstd::basic_ios<CharT,Traits>)[edit]
      manages associated stream buffer
      (public member function ofstd::basic_ios<CharT,Traits>)[edit]
      manages tied stream
      (public member function ofstd::basic_ios<CharT,Traits>)[edit]
      narrows characters
      (public member function ofstd::basic_ios<CharT,Traits>)[edit]
      widens characters
      (public member function ofstd::basic_ios<CharT,Traits>)[edit]

      Inherited fromstd::ios_base

      Member functions

      Formatting
      manages format flags
      (public member function ofstd::ios_base)[edit]
      sets specific format flag
      (public member function ofstd::ios_base)[edit]
      clears specific format flag
      (public member function ofstd::ios_base)[edit]
      manages decimal precision of floating point operations
      (public member function ofstd::ios_base)[edit]
      manages field width
      (public member function ofstd::ios_base)[edit]
      Locales
      sets locale
      (public member function ofstd::ios_base)[edit]
      returns current locale
      (public member function ofstd::ios_base)[edit]
      Internal extensible array
      [static]
      		 returns a program-wide unique integer that is safe to use as index topword() andiword()
      (public static member function ofstd::ios_base)[edit]
      resizes the private storage if necessary and access to thelong element at the given index
      (public member function ofstd::ios_base)[edit]
      resizes the private storage if necessary and access to thevoid* element at the given index
      (public member function ofstd::ios_base)[edit]
      Miscellaneous
      registers event callback function
      (public member function ofstd::ios_base)[edit]
      sets whether C++ and C I/O libraries are interoperable
      (public static member function ofstd::ios_base)[edit]
      Member classes
      stream exception
      (public member class ofstd::ios_base)[edit]
      initializes standard stream objects
      (public member class ofstd::ios_base)[edit]

      Member types and constants

      Type Explanation
      stream open mode type

      The following constants are also defined:

      Constant Explanation[edit]
      app seek to the end of stream before each write[edit]
      binary open inbinary mode[edit]
      in open for reading[edit]
      out open for writing[edit]
      trunc discard the contents of the stream when opening[edit]
      ate seek to the end of stream immediately after open[edit]
      noreplace(C++23) open in exclusive mode[edit]

      (typedef)[edit]
      formatting flags type

      The following constants are also defined:

      Constant Explanation[edit]
      dec use decimal base for integer I/O: seestd::dec[edit]
      oct use octal base for integer I/O: seestd::oct[edit]
      hex use hexadecimal base for integer I/O: seestd::hex[edit]
      basefielddec| oct| hex. Useful for masking operations[edit]
      left left adjustment (adds fill characters to the right): seestd::left[edit]
      right right adjustment (adds fill characters to the left): seestd::right[edit]
      internal internal adjustment (adds fill characters to the internal designated point): seestd::internal[edit]
      adjustfieldleft| right| internal. Useful for masking operations[edit]
      scientific generate floating point types using scientific notation, or hex notation if combined withfixed: seestd::scientific[edit]
      fixed generate floating point types using fixed notation, or hex notation if combined withscientific: seestd::fixed[edit]
      floatfieldscientific| fixed. Useful for masking operations[edit]
      boolalpha insert and extractbool type in alphanumeric format: seestd::boolalpha[edit]
      showbase generate a prefix indicating the numeric base for integer output, require the currency indicator in monetary I/O: seestd::showbase[edit]
      showpoint generate a decimal-point character unconditionally for floating-point number output: seestd::showpoint[edit]
      showpos generate a+ character for non-negative numeric output: seestd::showpos[edit]
      skipws skip leading whitespace before certain input operations: seestd::skipws[edit]
      unitbuf flush the output after each output operation: seestd::unitbuf[edit]
      uppercase replace certain lowercase letters with their uppercase equivalents in certain output operations: seestd::uppercase[edit]

      (typedef)[edit]
      state of the stream type

      The following constants are also defined:

      Constant Explanation[edit]
      goodbit no error[edit]
      badbit irrecoverable stream error[edit]
      failbit input/output operation failed (formatting or extraction error)[edit]
      eofbit associated input sequence has reached end-of-file[edit]

      (typedef)[edit]
      seeking direction type

      The following constants are also defined:

      Constant Explanation[edit]
      beg the beginning of a stream[edit]
      end the ending of a stream[edit]
      cur the current position of stream position indicator[edit]

      (typedef)[edit]
      specifies event type
      (enum)[edit]
      callback function type
      (typedef)[edit]
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