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.
putc — put a byte on a stream
int putc(int c, 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 putc() function shall be equivalent to fputc(),
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
Refer to fputc().
The following sections are informative.
Since it may be implemented as a macro, putc() may treat a stream
argument with side-effects incorrectly. In particular,
putc(c,*f++) does not necessarily work correctly.
Therefore, use of this function is not recommended in such situations;
fputc() should be used instead.
Section 2.5, Standard I/O Streams, fputc()
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 .
Any typographical or formatting errors that appear in this page
are most likely to have been introduced during the conversion of the source
files to man page format. To report such errors, see