Standard C Library Functions fputc(3C)
NAME
fputc, putc, putcunlocked, putchar, putcharunlocked, putw
- put a byte on a stream
SYNOPSIS
#include
int fputc(int c, FILE *stream);
int putc(int c, FILE *stream);
int putcunlocked(int c, FILE *stream);
int putchar(int c);
int putcharunlocked(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 stctime and stmtime 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.
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Standard C Library Functions fputc(3C)
The putcunlocked() and putcharunlocked() 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 stctime and stmtime 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(),
putcunlocked(), putchar(), and putcharunlocked() 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.
ERORS
The fputc(), putc(), putcunlocked(), putchar(),
putcharunlocked(), and putw() functions will fail if either
the stream is unbuffered or the stream's buffer needs to be
flushed, and:
EAGAIN The ONONBLOCK 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.
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Standard C Library Functions fputc(3C)
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 attempt-
ing to write to its controlling terminal, TOSTOP
is set, the process is neither ignoring nor block-
ing SIGTOU 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
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(), putcunlocked(), putchar(),
putcharunlocked(), 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(), putcunlocked(), putchar(),
and putcharunlocked() macros. To get the function form, the
macro name must be undefined (for example, #undef putc).
When the macro forms are used, putc() and putcunlocked()
evaluate the stream argument more than once. In particular,
putc(c, *f]); does not work sensibly. The fputc() function
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Standard C Library Functions fputc(3C)
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.
ATRIBUTES
See attributes(5) for descriptions of the following attri-
butes:
ATRIBUTE TYPE ATRIBUTE VALUE
Interface Stability fputc(), putc(),
putcunlocked(), putchar(),
and putcharunlocked() are
Standard.
MT-Level See NOTES below.
SEE ALSO
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), standards(5)
NOTES
The fputc(), putc(), putchar(), and putw() routines are MT-
Safe in multithreaded applications. The putcunlocked() and
putcharunlocked() routines are unsafe in multithreaded
applications.
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