1FGETC(P) POSIX Programmer's Manual FGETC(P)
2
6 fgetc - get a byte from a stream
7
9 #include <stdio.h>
10 int fgetc(FILE *stream);
12
15 If the end-of-file indicator for the input stream pointed to by stream
16 is not set and a next byte is present, the fgetc() function shall
17 obtain the next byte as an unsigned char converted to an int, from the
18 input stream pointed to by stream, and advance the associated file
19 position indicator for the stream (if defined). Since fgetc() operates
20 on bytes, reading a character consisting of multiple bytes (or "a
21 multi-byte character") may require multiple calls to fgetc().
22 The fgetc() function may mark the st_atime field of the file associated
24 with stream for update. The st_atime field shall be marked for update
25 by the first successful execution of fgetc(), fgets(), fgetwc(),
26 fgetws(), fread(), fscanf(), getc(), getchar(), gets(), or scanf()
27 using stream that returns data not supplied by a prior call to ungetc()
28 or ungetwc().
29
31 Upon successful completion, fgetc() shall return the next byte from the
32 input stream pointed to by stream. If the end-of-file indicator for the
33 stream is set, or if the stream is at end-of-file, the end-of-file
34 indicator for the stream shall be set and fgetc() shall return EOF. If
35 a read error occurs, the error indicator for the stream shall be set,
36 fgetc() shall return EOF, and shall set errno to indicate the error.
37
39 The fgetc() function shall fail if data needs to be read and:
40 EAGAIN The O_NONBLOCK flag is set for the file descriptor underlying
42 stream and the process would be delayed in the fgetc() opera‐
43 tion.
44 EBADF The file descriptor underlying stream is not a valid file
46 descriptor open for reading.
47 EINTR The read operation was terminated due to the receipt of a sig‐
49 nal, and no data was transferred.
50 EIO A physical I/O error has occurred, or the process is in a back‐
52 ground process group attempting to read from its controlling
53 terminal, and either the process is ignoring or blocking the
54 SIGTTIN signal or the process group is orphaned. This error may
55 also be generated for implementation-defined reasons.
56 EOVERFLOW
58 The file is a regular file and an attempt was made to read at or
59 beyond the offset maximum associated with the corresponding
60 stream.
61 The fgetc() function may fail if:
64 ENOMEM Insufficient storage space is available.
66 ENXIO A request was made of a nonexistent device, or the request was
68 outside the capabilities of the device.
69 The following sections are informative.
72
74 None.
75
77 If the integer value returned by fgetc() is stored into a variable of
78 type char and then compared against the integer constant EOF, the com‐
79 parison may never succeed, because sign-extension of a variable of type
80 char on widening to integer is implementation-defined.
81 The ferror() or feof() functions must be used to distinguish between an
83 error condition and an end-of-file condition.
84
86 None.
87
89 None.
90
92 feof() , ferror() , fopen() , getchar() , getc() , the Base Definitions
93 volume of IEEE Std 1003.1-2001, <stdio.h>
94
96 Portions of this text are reprinted and reproduced in electronic form
97 from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
98 -- Portable Operating System Interface (POSIX), The Open Group Base
99 Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
100 Electrical and Electronics Engineers, Inc and The Open Group. In the
101 event of any discrepancy between this version and the original IEEE and
102 The Open Group Standard, the original IEEE and The Open Group Standard
103 is the referee document. The original Standard can be obtained online
104 at http://www.opengroup.org/unix/online.html .
105IEEE/The Open Group 2003 FGETC(P)