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.\"	From: @(#)err.3	8.1 (Berkeley) 6/9/93
.\"	$Id: err.3,v 1.1 1997/02/27 07:32:21 gdr Exp $
.\"
.TH ERR 3 "April 13, 1995" GNO "Library Routines"
.SH NAME
.BR err ,
.BR verr ,
.BR errx ,
.BR verrx ,
.BR warn ,
.BR vwarn ,
.BR warnx ,
.BR vwarnx ,
.BR err_set_file ,
.BR err_set_exit
\- formatted error messages
.SH SYNOPSIS
.nf
#include <err.h>

void err (int \fIeval\fR, const char *\fIfmt\fR, ...);
void verr (int \fIeval\fR, const char *\fIfmt\fR, va_list \fIargs\fR);
void errx (int \fIeval\fR, const char *\fIfmt\fR, ...);
void verrx (int \fIeval\fR, const char *\fIfmt\fR, va_list \fIargs\fR);
void warn (const char *\fIfmt\fR, ...);
void vwarn (const char *\fIfmt\fR, va_list \fIargs\fR);
void warnx (const char *\fIfmt\fR, ...);
void vwarnx (const char *\fIfmt\fR, va_list \fIargs\fR);
void err_set_file (void *\fIfp\fR);
void err_set_exit (void (*\fIexitf\fR)(int));
.fi
.SH DESCRIPTION
The
.BR err 
and
.BR warn 
family of functions display a formatted error message on the standard
error output, or on another file specified using the
.BR err_set_file 
function.
In all cases, the last component of the program name, a colon character,
and a space are output.
If the
.IR fmt
argument is not NULL, the formatted error message, a colon character,
and a space are output.
In the case of the
.BR err ,
.BR verr ,
.BR warn ,
and
.BR vwarn 
functions, the error message string affiliated with the current value of
the global variable
.IR errno 
is output.
In all cases, the output is followed by a newline character.
.LP
The
.BR err ,
.BR verr ,
.BR errx ,
and
.BR verrx 
functions do not return, but exit with the value of the argument
.RI ( eval )
The
.BR err_set_exit 
function can be used to specify a function which is called before
.BR exit (3)
to perform any necessary cleanup; passing a null function pointer for
.IR exitf
resets the hook to do nothing.
.SH EXAMPLES
Display the current errno information string and exit:
.RS
.nf

if ((p = malloc(size)) == NULL)
	err(1, NULL);
if ((fd = open(file_name, O_RDONLY, 0)) == -1)
	err(1, "%s", file_name);

.fi
.RE
.LP
Display an error message and exit:
.RS
.nf

if (tm.tm_hour < START_TIME)
	errx(1, "too early, wait until %s", start_time_string);

.fi
.RE
.LP
Warn of an error:
.RS
.nf

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);

.fi
.RE
.SH "SEE ALSO"
.BR exit (3),
.BR strerror (3)
.SH HISTORY
The
.BR err 
and
.BR warn 
functions first appeared in 4.4BSD.