putchar_unlocked(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 (con-
verted 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. This
error may also be returned under implementation-
dependent 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 process.
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 ord-
ering, 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.
When a UFS file system is mounted with logging enabled, file
system transactions that free blocks from files might not
actually add those freed blocks to the file system's free
list until some unspecified time in the future. This
behavior improves file system performance but does not con-
form to the POSIX, Single UNIX Specification, SPARC Confor-
mance Definition, System V Application Binary Interface,
System V Interface Definition, and X/Open Portability Guide
Standards, which require that freed space be available
immediately. To enable standards conformance regarding file
deletions or to address the problem of not being able to
grow files on a relatively full UFS file system even after
files have been deleted, disable UFS logging (see
mount_ufs(1M).
ATTRIBUTES
See attributes(5) for descriptions of the following attri-
butes:
____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|_____________________________|_____________________________|
| MT-Level | See NOTES below. |
|_____________________________|_____________________________|
SEE ALSO
mount_ufs(1M), getrlimit(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)
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.
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