.\"	$OpenBSD: ERR_error_string.3,v 1.4 2016/11/23 17:55:31 schwarze Exp $
.\"	OpenSSL b97fdb57 Nov 11 09:33:09 2016 +0100
.\"
.\" This file was written by Ulf Moeller <ulf@openssl.org>.
.\" Copyright (c) 2000, 2004 The OpenSSL Project.  All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" 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 acknowledgment:
.\"    "This product includes software developed by the OpenSSL Project
.\"    for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
.\"
.\" 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
.\"    endorse or promote products derived from this software without
.\"    prior written permission. For written permission, please contact
.\"    openssl-core@openssl.org.
.\"
.\" 5. Products derived from this software may not be called "OpenSSL"
.\"    nor may "OpenSSL" appear in their names without prior written
.\"    permission of the OpenSSL Project.
.\"
.\" 6. Redistributions of any form whatsoever must retain the following
.\"    acknowledgment:
.\"    "This product includes software developed by the OpenSSL Project
.\"    for use in the OpenSSL Toolkit (http://www.openssl.org/)"
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
.\" EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
.\" PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
.\" ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
.\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
.\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
.\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
.\" OF THE POSSIBILITY OF SUCH DAMAGE.
.\"
.Dd $Mdocdate: November 23 2016 $
.Dt ERR_ERROR_STRING 3
.Os
.Sh NAME
.Nm ERR_error_string ,
.Nm ERR_error_string_n ,
.Nm ERR_lib_error_string ,
.Nm ERR_func_error_string ,
.Nm ERR_reason_error_string
.Nd obtain human-readable OpenSSL error messages
.Sh SYNOPSIS
.In openssl/err.h
.Ft char *
.Fo ERR_error_string
.Fa "unsigned long e"
.Fa "char *buf"
.Fc
.Ft void
.Fo ERR_error_string_n
.Fa "unsigned long e"
.Fa "char *buf"
.Fa "size_t len"
.Fc
.Ft const char *
.Fo ERR_lib_error_string
.Fa "unsigned long e"
.Fc
.Ft const char *
.Fo ERR_func_error_string
.Fa "unsigned long e"
.Fc
.Ft const char *
.Fo ERR_reason_error_string
.Fa "unsigned long e"
.Fc
.Sh DESCRIPTION
.Fn ERR_error_string
generates a human-readable string representing the error code
.Fa e
and places it in
.Fa buf .
.Fa buf
must be at least 256 bytes long.
If
.Fa buf
is
.Dv NULL ,
the error string is placed in a static buffer.
Note that this function is not thread-safe and does no checks on
the size of the buffer; use
.Fn ERR_error_string_n
instead.
.Pp
.Fn ERR_error_string_n
is a variant of
.Fn ERR_error_string
that writes at most
.Fa len
characters (including the terminating NUL) and truncates the string
if necessary.
For
.Fn ERR_error_string_n ,
.Fa buf
may not be
.Dv NULL .
.Pp
The string will have the following format:
.Pp
.Dl error:[error code]:[library name]:[function name]:[reason string]
.Pp
The error code is an 8-digit hexadecimal number.
The library name, the function name, and the reason string are ASCII
text.
.Pp
.Fn ERR_lib_error_string ,
.Fn ERR_func_error_string ,
and
.Fn ERR_reason_error_string
return the library name, the function name, and the reason string,
respectively.
.Pp
The OpenSSL error strings should be loaded by calling
.Xr ERR_load_crypto_strings 3
or, for SSL applications,
.Xr SSL_load_error_strings 3
first.
If there is no text string registered for the given error code, the
error string will contain the numeric code.
.Pp
.Xr ERR_print_errors 3
can be used to print all error codes currently in the queue.
.Sh RETURN VALUES
.Fn ERR_error_string
returns a pointer to a static buffer containing the string if
.Fa buf
is
.Dv NULL ,
or
.Fa buf
otherwise.
.Pp
.Fn ERR_lib_error_string ,
.Fn ERR_func_error_string ,
and
.Fn ERR_reason_error_string
return the strings, or
.Dv NULL
if none is registered for the error code.
.Sh SEE ALSO
.Xr ERR 3 ,
.Xr ERR_get_error 3 ,
.Xr ERR_load_crypto_strings 3 ,
.Xr ERR_print_errors 3 ,
.Xr SSL_load_error_strings 3
.Sh HISTORY
.Fn ERR_error_string
is available in all versions of SSLeay and OpenSSL.
.Fn ERR_error_string_n
was added in OpenSSL 0.9.6.