Add documentation.
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.\" $NetBSD: com_err.3,v 1.1 2001/11/21 05:39:49 gmcgarry Exp $
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.\"
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.\" Copyright (c) 2001 The NetBSD Foundation, Inc.
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.\" All rights reserved.
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.\"
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.\" This code is derived from software contributed to The NetBSD Foundation
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.\" by Gregory McGarry.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the NetBSD
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.\" Foundation, Inc. and its contributors.
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.\" 4. Neither the name of The NetBSD Foundation nor the names of its
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.\" contributors may be used to endorse or promote products derived
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.\" from this software without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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.\" POSSIBILITY OF SUCH DAMAGE.
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.\"
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.Dd November 21, 2001
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.Dt COM_ERR 3
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.Os
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.Sh NAME
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.Nm com_err ,
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.Nm com_err_va ,
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.Nm error_message ,
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.Nm error_table_name ,
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.Nm init_error_table ,
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.Nm set_com_err_hook ,
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.Nm reset_com_err_hook
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.Nd common error display library
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.Sh LIBRARY
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Common Error Library (libcom_err, -lcom_err)
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.Sh SYNOPSIS
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.Fd #include <stdio.h>
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.Fd #include <stdarg.h>
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.Fd #include <krb5/com_err.h>
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.Fd #include \&"XXX_err.h\&"
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.Pp
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typedef void (*errf)(const char *, long, const char *, ...);
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.Ft void
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.Fn com_err "const char *whoami" "long code" "const char *format" "..."
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.Ft void
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.Fn com_err_va "const char *whoami" "long code" "const char *format" "..."
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.Ft const char *
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.Fn error_message "long code"
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.Ft const char *
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.Fn error_table_name "int num"
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.Ft int
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.Fn init_error_table "const char **msgs" "long base" "int count"
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.Ft errf
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.Fn set_com_err_hook "errf func"
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.Ft errf
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.Fn reset_com_err_hook ""
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.Ft void
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.Fn add_to_error_table "struct et_list *new_table"
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.Sh DESCRIPTION
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The
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.Nm
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library provides a common error-reporting mechanism for defining and
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accessing error codes and descriptions for application software
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packages. Error descriptions are defined in a table and error codes
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are used to index the table. The error table, the descriptions and
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the error codes are generated using
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.Xr compile_et 1 .
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.Pp
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The error table is registered with the
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.Nm
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library by calling its initialisation function defined in its header
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file. The initialisation function is generally defined as
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.Fn initialize_<name>_error_table ,
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where
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.Em name
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is the name of the error table.
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.Pp
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Any variable which is to contain an error code should be declared
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.Em <name>_error_number
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where
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.Em name
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is the name of the error table.
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.Sh FUNCTIONS
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The following functions are available to the application developer:
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.Bl -tag -width compact
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.It Fn com_err "whoami" "code" "format" "..."
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Displays an error message on standard error composed of the
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.Fa whoami
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string, which should specify the program name, followed by an error
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message generated from
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.Fa code ,
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and a string produced using the
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.Xr printf 3
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.Fa format
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string and any following arguments. If
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.Fa format
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is NULL, the formatted message will not be
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printed. The argument
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.Fa format
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may not be omitted.
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.It Fn com_err_va "whoami" "code" "format" "va_list args"
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This routine provides an interface, equivalent to
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.Fn com_err ,
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which may be used by higher-level variadic functions (functions which
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accept variable numbers of arguments).
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.It Fn error_message "code"
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Returns the character string error message associate with
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.Fa code .
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If
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.Fa code is associated with an unknown error table, or if
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.Fa code
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is associated with a known error table but is not in the table, a
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string of the form `Unknown code XXXX NN' is returned, where XXXX is
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the error table name produced by reversing the compaction performed on
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the error table number implied by that error code, and NN is the
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offset from that base value.
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.Pp
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Although this routine is available for use when needed, its use should
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be left to circumstances which render
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.Fn com_err
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unusable.
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.It Fn error_table_name "num"
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Convert a machine-independent error table number
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.Fa num
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into an error table name.
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.It Fn init_error_table "msgs" "base" "count"
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Initialise the internal error table with the array of character string
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error messages in
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.Fa msgs
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of length
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.Fa count .
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The error codes are assigned incrementally from
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.Fa base .
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This function is useful for using the error-reporting mechanism with
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custom error tables that have not been generated with
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.Xr compile_et 1 .
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Although this routine is available for use when needed, its use should
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be restricted.
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.It Fn set_com_err_hook "func"
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Provides a hook into the
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.Nm
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library to allow the routine
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.Fa func
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to be dynamically substituted for
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.Fn com_err .
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After
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.Fn set_com_err_hook
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has been called, calls to
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.Fn com_err
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will turn into calls to the new hook routine. This function is
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intended to be used in daemons to use a routine which calls
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.Xr syslog 3 ,
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or in a window system application to pop up a dialogue box.
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.It Fn reset_com_err_hook ""
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Turns off the hook set in
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.Fn set_com_err_hook .
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.Ft void
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.Fn add_to_error_table "struct et_list *new_table"
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Add the error table, its messages strings and error codes in
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.Fa new_table
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to the internal error table.
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.El
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.Sh EXAMPLE
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The following is an example using the table defined in
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.Xr compile_et 1 :
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.Pp
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.Bd -literal
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#include <stdio.h>
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#include <stdarg.h>
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#include <syslog.h>
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#include "test_err.h"
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void
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hook(const char *whoami, long code,
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const char *format, va_list args)
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{
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char buffer[BUFSIZ];
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static int initialized = 0;
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if (!initialized) {
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openlog(whoami, LOG_NOWAIT, LOG_DAEMON);
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initialized = 1;
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}
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vsprintf(buffer, format, args);
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syslog(LOG_ERR, "%s %s", error_message(code), buffer);
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}
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int
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main(int argc, char *argv[])
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{
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char *whoami = argv[0];
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initialize_test_error_table();
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com_err(whoami, TEST_INVAL, "before hook");
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set_com_err_hook(hook);
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com_err(whoami, TEST_IO, "after hook");
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return (0);
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}
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.Ed
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.Sh SEE ALSO
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.Xr compile_et 1
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