.\" Copyright (c) 1993 The Regents of the University of California.
.\" All rights reserved.
.\"
.\" %sccs.include.redist.roff%
.\"
.\"	@(#)err.3	5.3 (Berkeley) 06/09/93
.\"
.Dd ""
.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.
In the case of the
.Fn err ,
.Fn verr ,
.Fn warn ,
and
.Fn vwarn
functions, 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 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
.Sh SEE ALSO
.Xr strerror 3
.Sh HISTORY
The
.Fn err
and
.Fn warn
functions first appeared in 4.4BSD.