1FGETC(3P) POSIX Programmer's Manual FGETC(3P)
2
6 This manual page is part of the POSIX Programmer's Manual. The Linux
7 implementation of this interface may differ (consult the corresponding
8 Linux manual page for details of Linux behavior), or the interface may
9 not be implemented on Linux.
10
13 fgetc — get a byte from a stream
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16 #include <stdio.h>
17 int fgetc(FILE *stream);
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21 The functionality described on this reference page is aligned with the
22 ISO C standard. Any conflict between the requirements described here
23 and the ISO C standard is unintentional. This volume of POSIX.1‐2008
24 defers to the ISO C standard.
25 If the end-of-file indicator for the input stream pointed to by stream
27 is not set and a next byte is present, the fgetc() function shall
28 obtain the next byte as an unsigned char converted to an int, from the
29 input stream pointed to by stream, and advance the associated file
30 position indicator for the stream (if defined). Since fgetc() operates
31 on bytes, reading a character consisting of multiple bytes (or ``a
32 multi-byte character'') may require multiple calls to fgetc().
33 The fgetc() function may mark the last data access timestamp of the
35 file associated with stream for update. The last data access timestamp
36 shall be marked for update by the first successful execution of
37 fgetc(), fgets(), fread(), fscanf(), getc(), getchar(), getdelim(),
38 getline(), gets(), or scanf() using stream that returns data not sup‐
39 plied by a prior call to ungetc().
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42 Upon successful completion, fgetc() shall return the next byte from the
43 input stream pointed to by stream. If the end-of-file indicator for
44 the stream is set, or if the stream is at end-of-file, the end-of-file
45 indicator for the stream shall be set and fgetc() shall return EOF. If
46 a read error occurs, the error indicator for the stream shall be set,
47 fgetc() shall return EOF, and shall set errno to indicate the error.
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50 The fgetc() function shall fail if data needs to be read and:
51 EAGAIN The O_NONBLOCK flag is set for the file descriptor underlying
53 stream and the thread would be delayed in the fgetc() operation.
54 EBADF The file descriptor underlying stream is not a valid file
56 descriptor open for reading.
57 EINTR The read operation was terminated due to the receipt of a sig‐
59 nal, and no data was transferred.
60 EIO A physical I/O error has occurred, or the process is in a back‐
62 ground process group attempting to read from its controlling
63 terminal, and either the calling thread is blocking SIGTTIN or
64 the process is ignoring SIGTTIN or the process group of the
65 process is orphaned. This error may also be generated for
66 implementation-defined reasons.
67 EOVERFLOW
69 The file is a regular file and an attempt was made to read at or
70 beyond the offset maximum associated with the corresponding
71 stream.
72 The fgetc() function may fail if:
74 ENOMEM Insufficient storage space is available.
76 ENXIO A request was made of a nonexistent device, or the request was
78 outside the capabilities of the device.
79 The following sections are informative.
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83 None.
84
86 If the integer value returned by fgetc() is stored into a variable of
87 type char and then compared against the integer constant EOF, the com‐
88 parison may never succeed, because sign-extension of a variable of type
89 char on widening to integer is implementation-defined.
90 The ferror() or feof() functions must be used to distinguish between an
92 error condition and an end-of-file condition.
93
95 None.
96
98 None.
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101 Section 2.5, Standard I/O Streams, feof(), ferror(), fgets(), fread(),
102 fscanf(), getchar(), getc(), gets(), ungetc()
103 The Base Definitions volume of POSIX.1‐2008, <stdio.h>
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107 Portions of this text are reprinted and reproduced in electronic form
108 from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
109 -- Portable Operating System Interface (POSIX), The Open Group Base
110 Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
111 cal and Electronics Engineers, Inc and The Open Group. (This is
112 POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the
113 event of any discrepancy between this version and the original IEEE and
114 The Open Group Standard, the original IEEE and The Open Group Standard
115 is the referee document. The original Standard can be obtained online
116 at http://www.unix.org/online.html .
117 Any typographical or formatting errors that appear in this page are
119 most likely to have been introduced during the conversion of the source
120 files to man page format. To report such errors, see https://www.ker‐
121 nel.org/doc/man-pages/reporting_bugs.html .
122IEEE/The Open Group 2013 FGETC(3P)