xref: /netbsd-src/lib/libc/stdio/getc.3 (revision 045ae074b53aad0d60cb1cb650994dc16ec1a303)

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.\"     @(#)getc.3	8.1 (Berkeley) 6/4/93
.\"
.Dd September 2, 2019
.Dt GETC 3
.Os
.Sh NAME
.Nm fgetc ,
.Nm getc ,
.Nm getchar ,
.Nm getc_unlocked ,
.Nm getchar_unlocked ,
.Nm getw
.Nd get next character or word from input stream
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In stdio.h
.Ft int
.Fn fgetc "FILE *stream"
.Ft int
.Fn getc "FILE *stream"
.Ft int
.Fn getchar
.Ft int
.Fn getc_unlocked "FILE *stream"
.Ft int
.Fn getchar_unlocked
.Ft int
.Fn getw "FILE *stream"
.Sh DESCRIPTION
The
.Fn fgetc
function
obtains the next input character (if present) from the stream pointed at by
.Fa stream ,
or the next character pushed back on the stream via
.Xr ungetc 3 .
.Pp
The
.Fn getc
function
acts essentially identically to
.Fn fgetc ,
but is a macro that expands in-line.
.Pp
The
.Fn getchar
function
is equivalent to:
getc with the argument stdin.
.Pp
The
.Fn getc_unlocked
and
.Fn getchar_unlocked
functions provide functionality identical to that of
.Fn getc
and
.Fn getchar ,
respectively, but do not perform implicit locking of the streams they
operate on.
In multi-threaded programs they may be used
.Em only
within a scope in which the stream
has been successfully locked by the calling thread using either
.Xr flockfile 3
or
.Xr ftrylockfile 3 ,
and may later be released using
.Xr funlockfile 3 .
.Pp
The
.Fn getw
function
obtains the next
.Em int
(if present)
from the stream pointed at by
.Fa stream .
.Sh RETURN VALUES
If successful, these routines return the next requested object
from the
.Fa stream .
If the stream is at end-of-file or a read error occurs,
the routines return
.Dv EOF .
The routines
.Xr feof 3
and
.Xr ferror 3
must be used to distinguish between end-of-file and error.
If an error occurs, the global variable
.Va errno
is set to indicate the error.
The end-of-file condition is remembered, even on a terminal, and all
subsequent attempts to read will return
.Dv EOF
until the condition is cleared with
.Xr clearerr 3 .
.Sh SEE ALSO
.Xr ferror 3 ,
.Xr flockfile 3 ,
.Xr fopen 3 ,
.Xr fread 3 ,
.Xr ftrylockfile 3 ,
.Xr funlockfile 3 ,
.Xr putc 3 ,
.Xr ungetc 3
.Sh STANDARDS
The
.Fn fgetc ,
.Fn getc
and
.Fn getchar
functions
conform to
.St -ansiC .
The
.Fn getc_unlocked
and
.Fn getchar_unlocked
functions conform to
.St -p1003.1-96 .
.Sh HISTORY
The
.Fn getc
and
.Fn getw
functions appeared in
.At v1 .
.Sh BUGS
Since
.Dv EOF
is a valid integer value,
.Xr feof 3
and
.Xr ferror 3
must be used to check for failure after calling
.Fn getw .
The size and byte order of an
.Em int
varies from one machine to another, and
.Fn getw
is not recommended for portable applications.