OPENSSL_config(3)

     NAME
          OPENSSL_config, OPENSSL_no_config - simple OpenSSL
          configuration functions

     SYNOPSIS
           #include <openssl/conf.h>

           void OPENSSL_config(const char *config_name);
           void OPENSSL_no_config(void);


     DESCRIPTION
          OPENSSL_config() configures OpenSSL using the standard
          openssl.cnf configuration file name using config_name. If
          config_name is NULL then the default name openssl_conf will
          be used. Any errors are ignored. Further calls to
          OPENSSL_config() will have no effect. The configuration file
          format is documented in the conf(5) manual page.

          OPENSSL_no_config() disables configuration. If called before
          OPENSSL_config() no configuration takes place.

     NOTES
          It is strongly recommended that all new applications call
          OPENSSL_config() or the more sophisticated functions such as
          CONF_modules_load() during initialization (that is before
          starting any threads). By doing this an application does not
          need to keep track of all configuration options and some new
          functionality can be supported automatically.

          It is also possible to automatically call OPENSSL_config()
          when an application calls OPENSSL_add_all_algorithms() by
          compiling an application with the preprocessor symbol
          OPENSSL_LOAD_CONF #define'd. In this way configuration can
          be added without source changes.

          The environment variable OPENSSL_CONFIG can be set to
          specify the location of the configuration file.

          Currently ASN1 OBJECTs and ENGINE configuration can be
          performed future versions of OpenSSL will add new
          configuration options.

          There are several reasons why calling the OpenSSL
          configuration routines is advisable. For example new ENGINE
          functionality was added to OpenSSL 0.9.7.  In OpenSSL 0.9.7
          control functions can be supported by ENGINEs, this can be
          used (among other things) to load dynamic ENGINEs from
          shared libraries (DSOs).  However very few applications
          currently support the control interface and so very few can
          load and use dynamic ENGINEs. Equally in future more
          sophisticated ENGINEs will require certain control
          operations to customize them. If an application calls
          OPENSSL_config() it doesn't need to know or care about
          ENGINE control operations because they can be performed by
          editing a configuration file.

          Applications should free up configuration at application
          closedown by calling CONF_modules_free().

     RESTRICTIONS
          The OPENSSL_config() function is designed to be a very
          simple "call it and forget it" function. As a result its
          behaviour is somewhat limited. It ignores all errors
          silently and it can only load from the standard
          configuration file location for example.

          It is however much better than nothing. Applications which
          need finer control over their configuration functionality
          should use the configuration functions such as
          CONF_load_modules() directly.

     RETURN VALUES
          Neither OPENSSL_config() nor OPENSSL_no_config() return a
          value.

     SEE ALSO
          conf(5), CONF_load_modules_file(3), the
          CONF_modules_free(3),CONF_modules_free(3) manpage

     HISTORY
          OPENSSL_config() and OPENSSL_no_config() first appeared in
          OpenSSL 0.9.7