.\"	$OpenBSD: err.3,v 1.4 1997/08/08 23:14:51 millert Exp $
.\"
.\" Copyright (c) 1993
.\"	The Regents of the University of California.  All rights reserved.
.\"
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.\" 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.
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\"
.Dd August, 8, 1997
.Dt ERR 3
.Os BSD 4
.Sh NAME
.Nm err ,
.Nm verr ,
.Nm errx ,
.Nm verrx ,
.Nm warn ,
.Nm vwarn ,
.Nm warnx ,
.Nm vwarnx
.Nd formatted error messages
.Sh SYNOPSIS
.Fd #include <err.h>
.Ft void
.Fn err "int eval" "const char *fmt" "..."
.Ft void
.Fn verr "int eval" "const char *fmt" "va_list args"
.Ft void
.Fn errx "int eval" "const char *fmt" "..."
.Ft void
.Fn verrx "int eval" "const char *fmt" "va_list args"
.Ft void
.Fn warn "const char *fmt" "..."
.Ft void
.Fn vwarn "const char *fmt" "va_list args"
.Ft void
.Fn warnx "const char *fmt" "..."
.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.
In all cases, the last component of the program name, a colon character,
and a space are output.
If the
.Va fmt
argument is not NULL, the formatted error message, a colon character,
and a space are output.  The
.Va fmt
argument (and associated arguments) may be any format allowed by
.Xr printf 3
or a simple string.
.Pp
In the case of the
.Fn err ,
.Fn verr ,
.Fn warn ,
and
.Fn vwarn
functions only, the error message string affiliated with the current value of
the global variable
.Va errno 
is output.
In all cases, the output is followed by a newline character.
.Pp
The
.Fn err ,
.Fn verr ,
.Fn errx ,
and
.Fn verrx
functions do not return, but exit with the value of the argument
.Fa eval .
.Sh EXAMPLES
Display the current
.Va 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, 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
.Sh SEE ALSO
.Xr exit 3 ,
.Xr perror 3 ,
.Xr printf 3 ,
.Xr strerror 3
.Sh HISTORY
The
.Fn err
and
.Fn warn
functions first appeared in 
.Bx 4.4 .