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.TH FGETC "3P" 2013 "IEEE/The Open Group" "POSIX Programmer's Manual"

.SH PROLOG

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.

.SH NAME

fgetc

\(em get a byte from a stream

.SH SYNOPSIS

.LP

.nf

#include <stdio.h>

.P

int fgetc(FILE *\fIstream\fP);

.fi

.SH DESCRIPTION

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\(hy2008 defers to the ISO\ C standard.

.P

If the end-of-file indicator for the input stream pointed to by

.IR stream

is not set and a next byte is present, the

\fIfgetc\fR()

function shall obtain the next byte as an

.BR "unsigned char"

converted to an

.BR int ,

from the input stream pointed to by

.IR stream ,

and advance the associated file position indicator for the stream (if

defined). Since

\fIfgetc\fR()

operates on bytes, reading a character consisting of multiple bytes (or

``a multi-byte character'') may require multiple calls to

\fIfgetc\fR().

.P

The

\fIfgetc\fR()

function may mark the last data access timestamp of the file

associated with

.IR stream

for update. The last data access timestamp shall be marked for

update by the first successful execution of

\fIfgetc\fR(),

\fIfgets\fR(),

\fIfread\fR(),

\fIfscanf\fR(),

\fIgetc\fR(),

\fIgetchar\fR(),

\fIgetdelim\fR(),

\fIgetline\fR(),

\fIgets\fR(),

or

\fIscanf\fR()

using

.IR stream

that returns data not supplied by a prior call to

\fIungetc\fR().

.SH "RETURN VALUE"

Upon successful completion,

\fIfgetc\fR()

shall return the next byte from the input stream pointed to by

.IR stream .

If the end-of-file indicator for the stream is set, or if the

stream is at end-of-file, the end-of-file indicator for the

stream shall be set and

\fIfgetc\fR()

shall return EOF. If a read error occurs, the error indicator for the

stream shall be set,

\fIfgetc\fR()

shall return EOF,

and shall set

.IR errno

to indicate the error.

.SH ERRORS

The

\fIfgetc\fR()

function shall fail if data needs to be read and:

.TP

.BR EAGAIN

The O_NONBLOCK flag is set for the file descriptor underlying

.IR stream

and the thread would be delayed in the

\fIfgetc\fR()

operation.

.TP

.BR EBADF

The file descriptor underlying

.IR stream

is not a valid file descriptor open for reading.

.TP

.BR EINTR

The read operation was terminated due to the receipt of a signal, and

no data was transferred.

.TP

.BR EIO

A physical I/O error has occurred, or the process is in a background

process group attempting to read from its controlling terminal, and

either the calling thread is blocking SIGTTIN or the process is ignoring

SIGTTIN or the process group of the process is orphaned.

This error may also be generated for implementation-defined reasons.

.TP

.BR EOVERFLOW

The file is a regular file and an attempt was made to read at or beyond

the offset maximum associated with the corresponding stream.

.P

The

\fIfgetc\fR()

function may fail if:

.TP

.BR ENOMEM

Insufficient storage space is available.

.TP

.BR ENXIO

A request was made of a nonexistent device, or the request was outside

the capabilities of the device.

.LP

.IR "The following sections are informative."

.SH EXAMPLES

None.

.SH "APPLICATION USAGE"

If the integer value returned by

\fIfgetc\fR()

is stored into a variable of type

.BR char

and then compared against the integer constant EOF, the comparison may

never succeed, because sign-extension of a variable of type

.BR char

on widening to integer is implementation-defined.

.P

The

\fIferror\fR()

or

\fIfeof\fR()

functions must be used to distinguish between an error condition and an

end-of-file condition.

.SH RATIONALE

None.

.SH "FUTURE DIRECTIONS"

None.

.SH "SEE ALSO"

.IR "Section 2.5" ", " "Standard I/O Streams",

.IR "\fIfeof\fR\^(\|)",

.IR "\fIferror\fR\^(\|)",

.IR "\fIfgets\fR\^(\|)",

.IR "\fIfread\fR\^(\|)",

.IR "\fIfscanf\fR\^(\|)",

.IR "\fIgetchar\fR\^(\|)",

.IR "\fIgetc\fR\^(\|)",

.IR "\fIgets\fR\^(\|)",

.IR "\fIungetc\fR\^(\|)"

.P

The Base Definitions volume of POSIX.1\(hy2008,

.IR "\fB<stdio.h>\fP"

.SH COPYRIGHT

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

https://www.kernel.org/doc/man-pages/reporting_bugs.html .