DragonFly On-Line Manual Pages
UNGETC(3) DragonFly Library Functions Manual UNGETC(3)
ungetc -- un-get character from input stream
Standard C Library (libc, -lc)
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-back
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 file-position indicator is decremented by
each successful call to ungetc(); if its value was 0 before a call, its
value is unspecified after the call.
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
fseek(3), getc(3), setvbuf(3), ungetwc(3)
The ungetc() function conforms to ISO/IEC 9899:1990 (``ISO C90'').
DragonFly 3.7 June 4, 1993 DragonFly 3.7