ungetc (3) - Linux Man Pages
ungetc: input of characters and strings
fgetc, fgets, getc, getchar, ungetc - input of characters and strings
#include <stdio.h> int fgetc(FILE *stream); char *fgets(char *s, int size, FILE *stream); int getc(FILE *stream); int getchar(void); int ungetc(int c, FILE *stream);
DESCRIPTIONfgetc() 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).
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).
RETURN VALUEfgetc(), getc(), and getchar() return the character read as an unsigned char cast to an int or EOF on end of file or error.
fgets() returns 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.
ATTRIBUTESFor an explanation of the terms used in this section, see attributes(7).
CONFORMING TOPOSIX.1-2001, POSIX.1-2008, C89, C99.
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.
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