UNGETC(3) NetBSD Library Functions Manual UNGETC(3)
ungetc -- un-get character from input stream
Standard C Library (libc, -lc)
#include <stdio.h> int ungetc(int c, FILE *stream);
The ungetc() function pushes the character c (converted to an unsigned char) back onto the input stream pointed to by stream. The pushed-backed characters will be returned by subsequent reads on the stream (in reverse order). A successful intervening call, using the same stream, to one of the file positioning functions (fseek(3), fsetpos(3), or rewind(3)) will discard the pushed back characters. One character of push-back is guaranteed, but as long as there is suffi- cient memory, an effectively infinite amount of pushback is allowed. If a character is successfully pushed-back, the end-of-file indicator for the stream is cleared.
The ungetc() function returns the character pushed-back after the conver- sion, or EOF if the operation fails. If the value of the argument c character equals EOF, the operation will fail and the stream will remain unchanged.
fseek(3), getc(3), setvbuf(3)
The ungetc() function conforms to ANSI X3.159-1989 (``ANSI C89'') and IEEE Std 1003.1-2001 (``POSIX.1'').
An ungetc() function appeared in Version 7 AT&T UNIX. NetBSD 9.0 April 30, 2010 NetBSD 9.0
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