=pod

=head1 NAME

ERR_error_string, ERR_error_string_n, ERR_lib_error_string,
ERR_func_error_string, ERR_reason_error_string - obtain human-readable
error message

=head1 SYNOPSIS

 #include <openssl/err.h>

 char *ERR_error_string(unsigned long e, char *buf);
 void ERR_error_string_n(unsigned long e, char *buf, size_t len);

 const char *ERR_lib_error_string(unsigned long e);
 const char *ERR_func_error_string(unsigned long e);
 const char *ERR_reason_error_string(unsigned long e);

=head1 DESCRIPTION

ERR_error_string() generates a human-readable string representing the
error code I<e>, and places it at I<buf>. I<buf> must be at least 120
bytes long. If I<buf> is B<NULL>, the error string is placed in a
static buffer.
ERR_error_string_n() is a variant of ERR_error_string() that writes
at most I<len> characters (including the terminating 0)
and truncates the string if necessary.
For ERR_error_string_n(), I<buf> may not be B<NULL>.

The string will have the following format:

 error:[error code]:[library name]:[function name]:[reason string]

I<error code> is an 8 digit hexadecimal number, I<library name>,
I<function name> and I<reason string> are ASCII text.

ERR_lib_error_string(), ERR_func_error_string() and
ERR_reason_error_string() return the library name, function
name and reason string respectively.

The OpenSSL error strings should be loaded by calling
L<ERR_load_crypto_strings(3)> or, for SSL
applications, L<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.

L<ERR_print_errors(3)> can be used to print
all error codes currently in the queue.

=head1 RETURN VALUES

ERR_error_string() returns a pointer to a static buffer containing the
string if I<buf> B<== NULL>, I<buf> otherwise.

ERR_lib_error_string(), ERR_func_error_string() and
ERR_reason_error_string() return the strings, and B<NULL> if
none is registered for the error code.

=head1 SEE ALSO

L<err(3)>, L<ERR_get_error(3)>,
L<ERR_load_crypto_strings(3)>,
L<SSL_load_error_strings(3)>
L<ERR_print_errors(3)>

=cut