This manual page is part of the POSIX Programmer's Manual. The Linux
implementation of this interface may differ (consult the
corresponding Linux manual page for details of Linux behavior), or
the interface may not be implemented on Linux.
The functionality described on this reference page is aligned with
the ISO C standard. Any conflict between the requirements described
here and the ISO C standard is unintentional. This volume of
POSIX.1‐2008 defers to the ISO C standard.
The fputc() function shall write 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 shall advance the indicator
appropriately. If the file cannot support positioning requests, or
if the stream was opened with append mode, the byte shall be appended
to the output stream.
The last data modification and last file status change timestamps of
the file shall be marked for update between the successful execution
of fputc() and the next successful completion of a call to fflush()
or fclose() on the same stream or a call to exit() or abort().
Upon successful completion, fputc() shall return the value it has
written. Otherwise, it shall return EOF, the error indicator for the
stream shall be set, and errno shall be set to indicate the error.
The fputc() function shall 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 thread 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.
EFBIG An attempt was made to write to a file that exceeds the file
size limit of the process.
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 calling thread is not
blocking SIGTTOU, the process is not ignoring SIGTTOU, and the
process group of the process is orphaned. This error may also
be returned under implementation-defined conditions.
ENOSPC There was no free space remaining on the device containing the
EPIPE An attempt is made to write to a pipe or FIFO that is not open
for reading by any process. A SIGPIPE signal shall also be
sent to the thread.
The fputc() function may fail if:
ENOMEM Insufficient storage space is available.
ENXIO A request was made of a nonexistent device, or the request was
outside the capabilities of the device.
The following sections are informative.
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The Open
Group Base Specifications Issue 7, Copyright (C) 2013 by the
Institute of Electrical and Electronics Engineers, Inc and The Open
Group. (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1
applied.) In the event of any discrepancy between this version and
the original IEEE and The Open Group Standard, the original IEEE and
The Open Group Standard is the referee document. The original
Standard can be obtained online at http://www.unix.org/online.html .
Any typographical or formatting errors that appear in this page are
most likely to have been introduced during the conversion of the
source files to man page format. To report such errors, see
IEEE/The Open Group 2013 FPUTC(3P)