Tribblix: manual page: fputc.3c

FPUTC(3C) Standard C Library Functions FPUTC(3C)

NAME

fputc, putc, putc_unlocked, putchar, putchar_unlocked, putw - put a
byte on a stream

SYNOPSIS

#include <stdio.h>

int fputc(int c, FILE *stream);

int putc(int c, FILE *stream);

int putc_unlocked(int c, FILE *stream);

int putchar(int c);

int putchar_unlocked(int c);

int putw(int w, FILE *stream);

DESCRIPTION

The fputc() function writes the byte specified by c (converted to an
unsigned char) to the output stream pointed to by stream, at the
position indicated by the associated file-position indicator for the
stream (if defined), and advances the indicator appropriately. If the
file cannot support positioning requests, or if the stream was opened
with append mode, the byte is appended to the output stream.

The st_ctime and st_mtime fields of the file will be marked for
update between the successful execution of fputc() and the next
successful completion of a call to fflush(3C) or fclose(3C) on the
same stream or a call to exit(3C) or abort(3C).

The putc() routine behaves like fputc(), except that it is
implemented as a macro. It runs faster than fputc(), but it takes up
more space per invocation and its name cannot be passed as an
argument to a function call.

The call putchar(c) is equivalent to putc(c, stdout). The putchar()
routine is implemented as a macro.

The putc_unlocked() and putchar_unlocked() routines are variants of
putc() and putchar(), respectively, that do not lock the stream. It
is the caller's responsibility to acquire the stream lock before
calling these routines and releasing the lock afterwards; see
flockfile(3C) and stdio(3C). These routines are implemented as
macros.

The putw() function writes the word (that is, type int) w to the
output stream (at the position at which the file offset, if defined,
is pointing). The size of a word is the size of a type int and varies
from machine to machine. The putw() function neither assumes nor
causes special alignment in the file.

The st_ctime and st_mtime fields of the file will be marked for
update between the successful execution of putw() and the next
successful completion of a call to fflush(3C) or fclose(3C) on the
same stream or a call to exit(3C) or abort(3C).

RETURN VALUES

Upon successful completion, fputc(), putc(), putc_unlocked(),
putchar(), and putchar_unlocked() return the value that was written.
Otherwise, these functions return EOF, the error indicator for the
stream is set, and errno is set to indicate the error.

Upon successful completion, putw() returns 0. Otherwise, it returns a
non-zero value, sets the error indicator for the associated stream,
and sets errno to indicate the error.

An unsuccessful completion will occur, for example, if the file
associated with stream is not open for writing or if the output file
cannot grow.

ERRORS

The fputc(), putc(), putc_unlocked(), putchar(), putchar_unlocked(),
and putw() functions will fail if either the stream is unbuffered or
the stream's buffer needs to be flushed, and:

EAGAIN
The O_NONBLOCK flag is set for the file descriptor
underlying stream and the process would be delayed in the
write operation.

EBADF
The file descriptor underlying stream is not a valid file
descriptor open for writing.

EFBIG
An attempt was made to write to a file that exceeds the
maximum file size or the process' file size limit.

EFBIG
The file is a regular file and an attempt was made to write
at or beyond the offset maximum.

EINTR
The write operation was terminated due to the receipt of a
signal, and no data was transferred.

EIO
A physical I/O error has occurred, or the process is a
member of a background process group attempting to write to
its controlling terminal, TOSTOP is set, the process is
neither ignoring nor blocking SIGTTOU and the process group
of the process is orphaned. stream was created by
open_wmemstream(3C) and a wide-character or byte sequence
buffered is invalid in the current locale. This error may
also be returned under implementation-dependent conditions.

ENOSPC
There was no free space remaining on the device containing
the file.

EPIPE
An attempt is made to write to a pipe or FIFO that is not
open for reading by any process. A SIGPIPE signal will also
be sent to the calling thread.

The fputc(), putc(), putc_unlocked(), putchar(), putchar_unlocked(),
and putw() functions may fail if:

ENOMEM
Insufficient storage space is available.

ENXIO
A request was made of a non-existent device, or the request
was outside the capabilities of the device.

USAGE

Functions exist for the putc(), putc_unlocked(), putchar(), and
putchar_unlocked() macros. To get the function form, the macro name
must be undefined (for example, #undef putc).

When the macro forms are used, putc() and putc_unlocked() evaluate
the stream argument more than once. In particular, putc(c, *f++);
does not work sensibly. The fputc() function should be used instead
when evaluating the stream argument has side effects.

Because of possible differences in word length and byte ordering,
files written using putw() are implementation-dependent, and possibly
cannot be read using getw(3C) by a different application or by the
same application running in a different environment.

The putw() function is inherently byte stream oriented and is not
tenable in the context of either multibyte character streams or wide-
character streams. Application programmers are encouraged to use one
of the character-based output functions instead.

ATTRIBUTES

NOTES

The fputc(), putc(), putchar(), and putw() routines are MT-Safe in
multithreaded applications. The putc_unlocked() and
putchar_unlocked() routines are unsafe in multithreaded applications.

March 25, 2020 FPUTC(3C)