这个问题实在不应该是问题，既然能上网，考虑一下google也会比在这里发问题强
ps:
NAME
fgetc, fgets, getc, getchar, gets, ungetc - input of characters and strings
SYNOPSIS
#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);
DESCRIPTION
fgetc() reads the next character from stream and returns it as an unsigned char cast to an int, or EOF on end of file or
error.
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 '\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 '\0' is stored after the last char-
acter 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 non-locking counterparts, see unlocked_stdio(3).
RETURN VALUE
fgetc(), getc() and getchar() return the character read as an unsigned char cast to an int or EOF on end of file or error.
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.
CONFORMING TO
C89, C99. LSB deprecates gets().
BUGS
Never use gets(). Because it is impossible to tell without knowing the data in advance how many characters gets() will read,
and because gets() will continue to store characters past the end of the buffer, it is extremely dangerous to use. It has
been used to break computer security. Use fgets() instead.
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.
SEE ALSO
read(2), write(2), ferror(3), fgetwc(3), fgetws(3), fopen(3), fread(3), fseek(3), getline(3), getwchar(3), puts(3), scanf(3),
ungetwc(3), unlocked_stdio(3)
GNU 1993-04-04 GETS(3)
ps:
NAME
fgetc, fgets, getc, getchar, gets, ungetc - input of characters and strings
SYNOPSIS
#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);
DESCRIPTION
fgetc() reads the next character from stream and returns it as an unsigned char cast to an int, or EOF on end of file or
error.
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 '\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 '\0' is stored after the last char-
acter 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 non-locking counterparts, see unlocked_stdio(3).
RETURN VALUE
fgetc(), getc() and getchar() return the character read as an unsigned char cast to an int or EOF on end of file or error.
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.
CONFORMING TO
C89, C99. LSB deprecates gets().
BUGS
Never use gets(). Because it is impossible to tell without knowing the data in advance how many characters gets() will read,
and because gets() will continue to store characters past the end of the buffer, it is extremely dangerous to use. It has
been used to break computer security. Use fgets() instead.
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.
SEE ALSO
read(2), write(2), ferror(3), fgetwc(3), fgetws(3), fopen(3), fread(3), fseek(3), getline(3), getwchar(3), puts(3), scanf(3),
ungetwc(3), unlocked_stdio(3)
GNU 1993-04-04 GETS(3)
