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 posi‐
tion 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 point‐
ing). 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 com‐
pletion 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 associ‐
ated 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. This
error may also be returned under implementation-depen‐
dent conditions.
ENOSPC There was no free space remaining on the device con‐
taining 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 evalu‐
ating 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 appli‐
cation running in a different environment.
The putw() function is inherently byte stream oriented and is not ten‐
able in the context of either multibyte character streams or wide-char‐
acter streams. Application programmers are encouraged to use one of the
character-based output functions instead.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
┌─────────────────────────────┬─────────────────────────────┐
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├─────────────────────────────┼─────────────────────────────┤
│Interface Stability │fputc(), putc(), │
│ │putc_unlocked(), putchar(), │
│ │and putchar_unlocked() are │
│ │Standard. │
├─────────────────────────────┼─────────────────────────────┤
│MT-Level │See NOTES below. │
└─────────────────────────────┴─────────────────────────────┘
SEE ALSOgetrlimit(2), ulimit(2)write(2), intro(3), abort(3C), exit(3C),
fclose(3C), ferror(3C), fflush(3C), flockfile(3C), fopen(3UCB),
printf(3C), putc(3C), puts(3C), setbuf(3C), stdio(3C), attributes(5),
standards(5)NOTES
The fputc(), putc(), putchar(), and putw() routines are MT-Safe in mul‐
tithreaded applications. The putc_unlocked() and putchar_unlocked()
routines are unsafe in multithreaded applications.
SunOS 5.10 1 Nov 2003 fputc(3C)
