C++ standard input functions comparison

Name	Header	Std	Description	Signature
getc	stdio	C89	reads single char or EOF(-1) from FILE	int getc(FILE *stream)
fgetc	stdio	C89	< same, just guaranteed to not be a macro >	int fgetc(FILE *stream)
getchar	stdio	C89	reads char from stdin but waits for EOL [EOL not extracted!]	int getchar()
getch	conio		reads ONE single char from stdin (keyboard) without waiting for EOL	int getch()
getche	conio		reads ONE single char from keyboard unbuffered with echo to screen	int getche()
kbhit	conio		checks whether keyboard press is waiting in the keyboard buffer returning a bool-like value (non-blocking)	int kbhit()
_getch	conio		< more ISO compatible names for getch()/getche()/kbhit() >	int _getch()
_getche	conio		< though un-underscored version could be more portable, cf. ncurses >	int _getche()
_kbhit	conio			int _kbhit()
_getchar_nolock	stdio		"nolock" is for "no protection against interference by other threads" (could be faster a bit)	int _getchar_nolock()
_getch_nolock	stdio		"nolock" is for "no protection against interference by other threads" (could be faster a bit)	int _getch_nolock()
_getche_nolock	stdio		"nolock" is for "no protection against interference by other threads" (could be faster a bit)	int _getche_nolock()

gets	stdio	C89	reads chars from stdin into char* until EOL/EOF, regardless of buffer size. Do not use it. Removed in C11.	char * gets( char *str )
gets_s	stdio	C11/C_BOUNDS	reads chars from stdin into char* until EOL/EOF, bounds-checked version [EOL extracted and dropped, not appended]	char * gets_s(char*, rsize_t)
fgets	stdio	C89	reads chars from FILE into char* until EOL/EOF (bounds-checked) [EOL extracted and appended to input]	char * fgets(char, int count, FILE)
scanf	stdio	C89	reads formatted from stdin [strings are delimited by any whitespace, which are not extracted and not appended]	int scanf(const char* format, ... )
fscanf	stdio	C89	reads formatted from FILE	int fscanf(FILE, const char format, ... )
sscanf	stdio	C89	reads formatted from char*	int sscanf(const char * buffer, const char * format, ... )
scanf_s	stdio	C11/C_BOUNDS	< bounds-checked versions of the above three >
fscanf_s	stdio	C11/C_BOUNDS
sscanf_s	stdio	C11/C_BOUNDS
getline	stdio	DM:TR	allocates/reallocates char** according to the size of chars to read (autogrow) [EOL extracted & appended]	ssize_t getline(char*, size_t, FILE*) [[like a reallocating fgets()]]
getdelim	stdio	DM:TR	< same as getline, just delimiter can be chosen >	ssize_t getdelim(char*, size_t, int delimiter, FILE*)
istream::peek	istream	C++98	reads one char from stream if possible without extracting it (or returns EOF), called with cin: waits for EOL like getchar()	int istream::peek()
istream::ignore	istream	C++98	extracts and discards characters from stream	istream& ignore( std::streamsize count = 1, int_type delim = Traits::eof() )
istream::get	istream	C++98	reads one char from stream if possible [[like getc()]]	int istream::get()
istream::get(char&)	istream	C++98	reads one char into arg if possible	istream& istream::get(char_type&)
istream::get(char*, count)	istream	C++98	reads char* until EOL/EOF bounds-checked [EOL not extracted]	istream& istream::get(char_type*, std::streamsize [, char_type delim])
istream::getline(char*, count)	istream	C++98	reads char* until EOL/EOF bounds-checked [EOL extracted and dropped]	istream& istream::getline(char_type*, std::streamsize count [, char_type delim])
std::getline(istream, string)	string	C++98/11	reads string until EOL/EOF autogrow [EOL extracted and dropped]	istream& std::getline(istream&[&] stream, string& str [, char_type delim])

istream::read	istream	C++98	reads buffer from stream
istream::readsome	istream	C++98	read at most N characters, but stops at the end of internal buffer (see also this )	std::streamsize istream::readsome( char_type* s, std::streamsize count )
cin.read(char*,1)	istream	C++98	reads one character, waits for EOL [EOL not extracted!] (basically a getc()/getchar() for streams)
cin.read(char*,N)	istream	C++98	reads N characters

istream::operator>>(datatype&)	istream	C++98	reads formatted from stream, datatype can be bool, [unsigned] short/int/long/long long, float, [long] double, void*	istream& operator>> (datatype& val)
istream::operator>>(streambuf&[, char_type delim])	istream	C++98	reads all available data (or data up to delim) to another stream	istream& operator>>( std::basic_streambuf<char_type,Traits>* sb )

Notes:

istream stands for std::basic_istream<char_type,Traits> everywhere, and
string is for std::basic_string<char_type>

This also means that for stream functions above the widechar (wchar_t) equivalents are the same, only instantiated with char_type=wchar_t instead of char_type=char.
ssize_t and std::streamsize can be thought to be the same, and the same stands for rsize_t and size_t also.

DM:TR: ISO C Dynamic Memory TR extensions: available if _STDC_ALLOC_LIB_, and then can be switched ON using _STDC_WANT_LIB_EXT2_ 1 before #include
C_BOUNDS: Bounds checked extensions: available if _STDC_LIB_EXT1_, and than can be switched ON using _STDC_WANT_LIB_EXT1_ 1 before #include

(these all prefixed & suffixed by double underscores)

std::istream::operator>> functions have their std namespace function template versions (std::operator>>) too

End-Of-Line extraction

fn	EOL	input	output	std	header
getchar	left	stdin	int	C89	stdio
scanf	left	stdin	char*	C89	stdio
fscanf	left	FILE	char*	C89	stdio
istream::get(char*)	left	stream	char*	C++98	istream
gets[_s]	dropped	stdin	char*	C89/11	stdio
istream::getline(char*)	dropped	stream	char*	C++98	istream
std::getline	dropped	stream	string	C++98	string
fgets	appended	FILE	char*	C89	stdio
getline DM	appended	FILE	char*	DM:TR	stdio

Widechar-equivalents (for non-stream functions)

function	widechar-equiv.	header
getc/fgetc	fgetwc	wchar
getchar	getwchar	wchar
_getch	_getwch	conio or wchar
_getche	_getwche	conio or wchar
_getchar_nolock ...	_getwchar_nolock ...	stdio or wchar
gets_s	_getws_s	stdio or wchar
fgets	fgetws	wchar
scanf/fscanf/sscanf	wscanf, fwscanf, swscanf	wchar
scanf_s/fscanf_s/sscanf_s	wscanf_s, fwscanf_s, swscanf_s	wchar
getline	getwline	stdio
detdelim	getwdelim	stdio