'\" t
.\" Copyright (c) 1993
.\"	The Regents of the University of California.  All rights reserved.
.\"
.\" SPDX-License-Identifier: BSD-4-Clause-UC
.\"
.\"	From: @(#)err.3	8.1 (Berkeley) 6/9/93
.\" $FreeBSD: src/lib/libc/gen/err.3,v 1.11.2.5 2001/08/17 15:42:32 ru Exp $
.\"
.\" 2011-09-10, mtk, Converted from mdoc to man macros
.\"
.TH err 3 2024-05-02 "Linux man-pages 6.8"
.SH NAME
err, verr, errx, verrx, warn, vwarn, warnx, vwarnx \- formatted error messages
.SH LIBRARY
Standard C library
.RI ( libc ", " \-lc )
.SH SYNOPSIS
.nf
.B #include <err.h>
.P
.BI "[[noreturn]] void err(int " eval ", const char *" fmt ", ...);"
.BI "[[noreturn]] void errx(int " eval ", const char *" fmt ", ...);"
.P
.BI "void warn(const char *" fmt ", ...);"
.BI "void warnx(const char *" fmt ", ...);"
.P
.B #include <stdarg.h>
.P
.BI "[[noreturn]] void verr(int " eval ", const char *" fmt ", va_list " args );
.BI "[[noreturn]] void verrx(int " eval ", const char *" fmt ", va_list " args );
.P
.BI "void vwarn(const char *" fmt ", va_list " args );
.BI "void vwarnx(const char *" fmt ", va_list " args );
.fi
.SH DESCRIPTION
The
.BR err ()
and
.BR 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
.I fmt
argument is not NULL, the
.BR printf (3)-like
formatted error message is output.
The output is terminated by a newline character.
.P
The
.BR err (),
.BR verr (),
.BR warn (),
and
.BR vwarn ()
functions append an error message obtained from
.BR strerror (3)
based on the global variable
.IR errno ,
preceded by another colon and space unless the
.I fmt
argument is
NULL.
.P
The
.BR errx ()
and
.BR warnx ()
functions do not append an error message.
.P
The
.BR err (),
.BR verr (),
.BR errx (),
and
.BR verrx ()
functions do not return, but exit with the value of the argument
.IR eval .
.SH ATTRIBUTES
For an explanation of the terms used in this section, see
.BR attributes (7).
.TS
allbox;
lbx lb lb
l l l.
Interface	Attribute	Value
T{
.na
.nh
.BR err (),
.BR errx (),
.BR warn (),
.BR warnx (),
.BR verr (),
.BR verrx (),
.BR vwarn (),
.BR vwarnx ()
T}	Thread safety	MT-Safe locale
.TE
.SH STANDARDS
BSD.
.SH HISTORY
.TP
.BR err ()
.TQ
.BR warn ()
4.4BSD.
.SH EXAMPLES
Display the current
.I errno
information string and exit:
.P
.in +4n
.EX
p = malloc(size);
if (p == NULL)
    err(EXIT_FAILURE, NULL);
fd = open(file_name, O_RDONLY, 0);
if (fd == \-1)
    err(EXIT_FAILURE, "%s", file_name);
.EE
.in
.P
Display an error message and exit:
.P
.in +4n
.EX
if (tm.tm_hour < START_TIME)
    errx(EXIT_FAILURE, "too early, wait until %s",
            start_time_string);
.EE
.in
.P
Warn of an error:
.P
.in +4n
.EX
fd = open(raw_device, O_RDONLY, 0);
if (fd == \-1)
    warnx("%s: %s: trying the block device",
            raw_device, strerror(errno));
fd = open(block_device, O_RDONLY, 0);
if (fd == \-1)
    err(EXIT_FAILURE, "%s", block_device);
.EE
.in
.SH SEE ALSO
.BR error (3),
.BR exit (3),
.BR perror (3),
.BR printf (3),
.BR strerror (3)