.\" Copyright (c) 1990, 1991, 1993
.\"	The Regents of the University of California.  All rights reserved.
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.\" This code is derived from software contributed to Berkeley by
.\" Chris Torek and the American National Standards Committee X3,
.\" on Information Processing Systems.
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.\" modification, are permitted provided that the following conditions
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.\"    may be used to endorse or promote products derived from this software
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.\"     @(#)putc.3	8.1 (Berkeley) 6/4/93
.\"
.Dd January 23, 2020
.Dt PUTC 3
.Os
.Sh NAME
.Nm fputc ,
.Nm fputc_unlocked ,
.Nm putc ,
.Nm putc_unlocked ,
.Nm putchar ,
.Nm putchar_unlocked ,
.Nm putw
.Nd output a character or word to a stream
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In stdio.h
.Ft int
.Fn fputc "int c" "FILE *stream"
.Ft int
.Fn fputc_unlocked "int c" "FILE *stream"
.Ft int
.Fn putc "int c" "FILE *stream"
.Ft int
.Fn putc_unlocked "int c" "FILE *stream"
.Ft int
.Fn putchar "int c"
.Ft int
.Fn putchar_unlocked "int c"
.Ft int
.Fn putw "int w" "FILE *stream"
.Sh DESCRIPTION
The
.Fn fputc
function
writes the character
.Fa c
(converted to an ``unsigned char'')
to the output stream pointed to by
.Fa stream .
.Pp
The
.Fn putc
macro acts essentially identically to
.Fn fputc ,
but is a macro that expands in-line.
It may evaluate
.Fa stream
more than once, so arguments given to
.Fn putc
should not be expressions with potential side effects.
.Pp
The
.Fn putchar
function
is identical to
.Fn putc
with an output stream of
.Dv stdout .
.Pp
The
.Fn putw
function
writes the specified
.Vt int
to the named output
.Fa stream .
.Pp
The
.Fn fputc_unlocked ,
.Fn putc_unlocked ,
and
.Fn putchar_unlocked
functions are equivalent to
.Fn fputc ,
.Fn putc ,
and
.Fn putchar
respectively,
except that the caller is responsible for locking the stream
with
.Xr flockfile 3
before calling them.
These functions may be used to avoid the overhead of locking the stream
for each character, and to avoid output being interspersed from multiple
threads writing to the same stream.
.Sh RETURN VALUES
The functions,
.Fn fputc ,
.Fn putc ,
.Fn putchar ,
.Fn putc_unlocked
and
.Fn putchar_unlocked
return the character written.
If an error occurs, the value
.Dv EOF
is returned.
The
.Fn putw
function
returns 0 on success;
.Dv EOF
is returned if
a write error occurs,
or if an attempt is made to write a read-only stream.
.Sh SEE ALSO
.Xr ferror 3 ,
.Xr flockfile 3 ,
.Xr fopen 3 ,
.Xr getc 3 ,
.Xr putwc 3 ,
.Xr stdio 3
.Sh STANDARDS
The functions
.Fn fputc ,
.Fn putc ,
and
.Fn putchar ,
conform to
.St -isoC .
The
.Fn putc_unlocked
and
.Fn putchar_unlocked
functions conform to
.St -p1003.1-2001 .
A function
.Fn putw
function appeared in
.At v6 .
.Sh BUGS
The size and byte order of an
.Vt int
varies from one machine to another, and
.Fn putw
is not recommended for portable applications.