freebsd/lib/libc/gen/err.3

.\" Copyright (c) 1993
.\"	The Regents of the University of California.  All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. All advertising materials mentioning features or use of this software
.\"    must display the following acknowledgement:
.\"	This product includes software developed by the University of
.\"	California, Berkeley and its contributors.
.\" 4. Neither the name of the University nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\"	From: @(#)err.3	8.1 (Berkeley) 6/9/93
.\" $FreeBSD$
.\"
.Dd March 6, 1999
.Dt ERR 3
.Os
.Sh NAME
.Nm err ,
.Nm verr ,
.Nm errc ,
.Nm verrc ,
.Nm errx ,
.Nm verrx ,
.Nm warn ,
.Nm vwarn ,
.Nm warnc ,
.Nm vwarnc ,
.Nm warnx ,
.Nm vwarnx ,
.Nm err_set_exit ,
.Nm err_set_file
.Nd formatted error messages
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.Fd #include <err.h>
.Ft void
.Fn err "int eval" "const char *fmt" "..."
.Ft void
.Fn err_set_exit "void (*exitf)(int)"
.Ft void
.Fn err_set_file "void *vfp"
.Ft void
.Fn errc "int eval" "int code" "const char *fmt" "..."
.Ft void
.Fn errx "int eval" "const char *fmt" "..."
.Ft void
.Fn warn "const char *fmt" "..."
.Ft void
.Fn warnc "int code" "const char *fmt" "..."
.Ft void
.Fn warnx "const char *fmt" "..."
.Fd #include <stdarg.h>
.Ft void
.Fn verr "int eval" "const char *fmt" "va_list args"
.Ft void
.Fn verrc "int eval" "int code" "const char *fmt" "va_list args"
.Ft void
.Fn verrx "int eval" "const char *fmt" "va_list args"
.Ft void
.Fn vwarn "const char *fmt" "va_list args"
.Ft void
.Fn vwarnc "int code" "const char *fmt" "va_list args"
.Ft void
.Fn vwarnx "const char *fmt" "va_list args"
.Sh DESCRIPTION
The
.Fn err
and
.Fn warn
family of functions display a formatted error message on the standard
error output, or on another file specified using the
.Fn err_set_file
function.
In all cases, the last component of the program name, a colon character,
and a space are output.
If the
.Fa fmt
argument is not NULL, the
.Xr printf 3
-like formatted error message is output.
The output is terminated by a newline character.
.Pp
The
.Fn err ,
.Fn errc ,
.Fn verr ,
.Fn verrc ,
.Fn warn ,
.Fn warnc ,
.Fn vwarn ,
and
.Fn vwarnc
functions append an error message obtained from
.Xr strerror 3
based on a code or the global variable
.Va errno ,
preceded by another colon and space unless the
.Fa fmt
argument is
.Dv NULL .
.Pp
In the case of the
.Fn errc ,
.Fn verrc ,
.Fn warnc ,
and
.Fn vwarnc
functions,
the
.Fa code
argument is used to look up the error message.
.Pp
The
.Fn err ,
.Fn verr ,
.Fn warn ,
and
.Fn vwarn
functions use the global variable
.Va errno
to look up the error message.
.Pp
The
.Fn errx
and
.Fn warnx
functions do not append an error message.
.Pp
The
.Fn err ,
.Fn verr ,
.Fn errc ,
.Fn verrc ,
.Fn errx ,
and
.Fn verrx
functions do not return, but exit with the value of the argument
.Fa eval .
The
.Fn err_set_exit
function can be used to specify a function which is called before
.Xr exit 3
to perform any necessary cleanup; passing a null function pointer for
.Va exitf
resets the hook to do nothing.
The
.Fn err_set_file
function sets the output stream used by the other functions.
Its
.Fa vfp
argument must be either a pointer to an open stream
(possibly already converted to void *)
or a null pointer
(in which case the output stream is set to standard error).
.Sh EXAMPLES
Display the current errno information string and exit:
.Bd -literal -offset indent
if ((p = malloc(size)) == NULL)
	err(1, NULL);
if ((fd = open(file_name, O_RDONLY, 0)) == -1)
	err(1, "%s", file_name);
.Ed
.Pp
Display an error message and exit:
.Bd -literal -offset indent
if (tm.tm_hour < START_TIME)
	errx(1, "too early, wait until %s", start_time_string);
.Ed
.Pp
Warn of an error:
.Bd -literal -offset indent
if ((fd = open(raw_device, O_RDONLY, 0)) == -1)
	warnx("%s: %s: trying the block device",
	    raw_device, strerror(errno));
if ((fd = open(block_device, O_RDONLY, 0)) == -1)
	err(1, "%s", block_device);
.Ed
.Pp
Warn of an error without using the global variable
.Va errno :
.Bd -literal -offset indent
error = my_function();	/* returns a value from <errno.h> */
if (error != 0)
	warnc(error, "my_function");
.Ed
.Sh SEE ALSO
.Xr exit 3 ,
.Xr printf 3 ,
.Xr strerror 3
.Sh HISTORY
The
.Fn err
and
.Fn warn
functions first appeared in
.Bx 4.4 .
The
.Fn err_set_exit
and
.Fn err_set_file
functions first appeared in
.Fx 2.1 .
The
.Fn errc
and
.Fn warnc
functions first appeared in
.Fx 3.0 .