1ungetc(3C) Standard C Library Functions ungetc(3C)
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6 ungetc - push byte back into input stream
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9 #include <stdio.h>
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11 int ungetc(int c, FILE *stream);
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15 The ungetc() function pushes the byte specified by c (converted to an
16 unsigned char) back onto the input stream pointed to by stream. The
17 pushed-back bytes will be returned by subsequent reads on that stream
18 in the reverse order of their pushing. A successful intervening call
19 (with the stream pointed to by stream) to a file-positioning function (
20 fseek(3C), fsetpos(3C) or rewind(3C)) discards any pushed-back bytes
21 for the stream. The external storage corresponding to the stream is
22 unchanged.
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25 Four bytes of push-back are guaranteed. If ungetc() is called too many
26 times on the same stream without an intervening read or file-position‐
27 ing operation on that stream, the operation may fail.
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30 If the value of c equals that of the macro EOF, the operation fails and
31 the input stream is unchanged.
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34 A successful call to ungetc() clears the end-of-file indicator for the
35 stream. The value of the file-position indicator for the stream after
36 reading or discarding all pushed-back bytes will be the same as it was
37 before the bytes were pushed back. The file-position indicator is
38 decremented by each successful call to ungetc(); if its value was 0
39 before a call, its value is indeterminate after the call.
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42 Upon successful completion, ungetc() returns the byte pushed back after
43 conversion. Otherwise it returns EOF.
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46 No errors are defined.
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49 See attributes(5) for descriptions of the following attributes:
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54 ┌─────────────────────────────┬─────────────────────────────┐
55 │ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
56 ├─────────────────────────────┼─────────────────────────────┤
57 │Interface Stability │Standard │
58 ├─────────────────────────────┼─────────────────────────────┤
59 │MT-Level │MT-Safe │
60 └─────────────────────────────┴─────────────────────────────┘
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63 read(2), Intro(3), __fsetlocking(3C), fseek(3C), fsetpos(3C), getc(3C),
64 setbuf(3C), stdio(3C), attributes(5), standards(5)
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68SunOS 5.11 10 Sep 2003 ungetc(3C)