xref: /freebsd/lib/libc/stdio/getc.3 (revision dc36d6f9bb1753f3808552f3afd30eda9a7b206a)

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.Dd April 4, 2020
.Dt GETC 3
.Os
.Sh NAME
.Nm fgetc ,
.Nm getc ,
.Nm getc_unlocked ,
.Nm getchar ,
.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 getc_unlocked "FILE *stream"
.Ft int
.Fn getchar void
.Ft int
.Fn getchar_unlocked void
.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
.Fn getc stdin .
.Pp
The
.Fn getw
function
obtains the next
.Vt int
(if present)
from the stream pointed at by
.Fa stream .
.Pp
The
.Fn getc_unlocked
and
.Fn getchar_unlocked
functions are equivalent to
.Fn getc
and
.Fn getchar
respectively,
except that the caller is responsible for locking the stream
with
.Xr flockfile 3
before calling them.
These functions may be used to avoid the overhead of locking the stream
for each character, and to avoid input being dispersed among multiple
threads reading from the same stream.
.Sh RETURN VALUES
If successful, these routines return the next requested object
from the
.Fa stream .
Character values are returned as an
.Vt "unsigned char"
converted to an
.Vt int .
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 getwc 3 ,
.Xr putc 3 ,
.Xr ungetc 3
.Sh STANDARDS
The
.Fn fgetc ,
.Fn getc ,
and
.Fn getchar
functions
conform to
.St -isoC .
The
.Fn getc_unlocked
and
.Fn getchar_unlocked
functions conform to
.St -p1003.1-2001 .
.Sh HISTORY
The
.Fn getc
and
.Fn getw
functions appeared in a similar form in
.At v1 ;
and were integrated into stdio in
.At v7 ;
.Fn getchar
in
.At v4 ;
and
.Fn fgetc
in
.At v7 .
.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
.Vt int
varies from one machine to another, and
.Fn getw
is not recommended for portable applications.