ungetc#
Synopsis#
#include <stdio.h>
int ungetc(int c, FILE *stream);
Status#
Partially implemented
Conformance#
IEEE Std 1003.1-2017
Description#
The ungetc() function shall push the byte specified by c (converted to a unsigned char) back onto the input stream
pointed to by stream. The pushed-back bytes shall be returned by subsequent reads on that stream in the reverse order of
their pushing. A successful intervening call (with the stream pointed to by stream) to a file-positioning function
(fseek(), fseeko(), fsetpos(), or rewind()) or fflush() shall discard any pushed-back bytes for the stream.
The external storage corresponding to the stream shall be unchanged.
One byte of push-back shall be provided. If ungetc() is called too many times on the same stream without an
intervening read or file-positioning operation on that stream, the operation may fail.
If the value of c equals that of the macro EOF, the operation shall fail and the input stream shall be left
unchanged.
A successful call to ungetc() shall clear the end-of-file indicator for the stream. The value of the file-position
indicator for the stream after all pushed-back bytes have been read, or discarded by calling fseek(), fseeko(),
fsetpos(), or rewind() (but not fflush()), shall be the same as it was before the bytes were pushed back. 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.
Return value#
Upon successful completion, ungetc() shall return the byte pushed back after conversion. Otherwise, it shall return
EOF.
Errors#
No errors are defined.
Tests#
Untested
Known bugs#
None