This manual page is part of the POSIX Programmer's Manual. The Linux
implementation of this interface may differ (consult the corresponding Linux
manual page for details of Linux behavior), or the interface may not be
implemented on Linux.
getc — get a byte from a stream
int getc(FILE *stream);
The functionality described on this reference page is aligned with the
ISO C standard. Any conflict between the requirements described here
and the ISO C standard is unintentional. This volume of
POSIX.1‐2017 defers to the ISO C standard.
The getc() function shall be equivalent to
fgetc(), except that if it is implemented as a macro it may
evaluate stream more than once, so the argument should never be an
expression with side-effects.
Refer to fgetc().
The following sections are informative.
If the integer value returned by getc() is stored into a variable of type
char and then compared against the integer constant EOF, the comparison
may never succeed, because sign-extension of a variable of type char on
widening to integer is implementation-defined.
Since it may be implemented as a macro, getc() may treat
incorrectly a stream argument with side-effects. In particular,
getc(*f++) does not necessarily work as expected. Therefore,
use of this function should be preceded by "#undefgetc" in
such situations; fgetc() could also be used.
Section 2.5, Standard I/O Streams, fgetc()
The Base Definitions volume of POSIX.1‐2017,
Portions of this text are reprinted and reproduced in electronic form from IEEE
Std 1003.1-2017, Standard for Information Technology -- Portable Operating
System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018
Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. In the event of any discrepancy between
this version and the original IEEE and The Open Group Standard, the original
IEEE and The Open Group Standard is the referee document. The original
Standard can be obtained online at http://www.opengroup.org/unix/online.html .
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