#include <stdio.h> int fgetc(FILE *stream); char *fgets(char *s, int size, FILE *stream); int getc(FILE *stream); int getchar(void); char *gets(char *s); int ungetc(int c, FILE *stream);
getc() is equivalent to fgetc() except that it may be implemented as a macro which evaluates stream more than once.
getchar() is equivalent to getc(stdin).
gets() reads a line from stdin into the buffer pointed to by s until either a terminating newline or EOF, which it replaces with a null byte ('\0'). No check for buffer overrun is performed (see BUGS below).
fgets() reads in at most one less than size characters from stream and stores them into the buffer pointed to by s. Reading stops after an EOF or a newline. If a newline is read, it is stored into the buffer. A terminating null byte ('\0') is stored after the last character in the buffer.
ungetc() pushes c back to stream, cast to unsigned char, where it is available for subsequent read operations. Pushed-back characters will be returned in reverse order; only one pushback is guaranteed.
Calls to the functions described here can be mixed with each other and with calls to other input functions from the stdio library for the same input stream.
For nonlocking counterparts, see unlocked_stdio(3).
gets() and fgets() return s on success, and NULL on error or when end of file occurs while no characters have been read.
ungetc() returns c on success, or EOF on error.
LSB deprecates gets(). POSIX.1-2008 marks gets() obsolescent. ISO C11 removes the specification of gets() from the C language, and since version 2.16, glibc header files don't expose the function declaration if the _ISOC11_SOURCE feature test macro is defined.
It is not advisable to mix calls to input functions from the stdio library with low-level calls to read(2) for the file descriptor associated with the input stream; the results will be undefined and very probably not what you want.