NAME

       efi_variables_supported,       efi_del_variable,      efi_get_variable,      efi_get_variable_attributes,
       efi_get_variable_size, efi_set_variable - manipulate UEFI variables

SYNOPSIS

       #include <efivar.h>

       int efi_variables_supported(void);
       int efi_del_variable(efi_guid_t guid, const char *name);

       int efi_get_variable(efi_guid_t guid, const char *name,
                            void **data, ssize_t *data_size,
                            uint32_t *attributes);

       int efi_get_variable_attributes(efi_guid_t guid, const char *name,
                                       uint32_t *attributes);

       int efi_get_variable_size(efi_guid_t guid, const char *name,
                                 size_t *size);

       int efi_append_variable(efi_guid_t guid, const char *name,
                            void *data, size_t data_size,
                            uint32_t attributes);

       int efi_set_variable(efi_guid_t guid, const char *name,
                            void *data, size_t data_size,
                            uint32_t attributes);

       int efi_set_variable(efi_guid_t guid, const char *name,
                            void *data, size_t data_size,
                            uint32_t attributes, mode_t mode);

       int efi_get_next_variable_name(efi_guid_t **guid, char **name);

       int efi_str_to_guid(const char *s, efi_guid_t *guid);

       int efi_guid_to_str(const efi_guid_t *guid, char **sp);

       int efi_name_to_guid(const char *name, efi_guid_t *guid);

       int efi_id_guid_to_guid(const char *id_guid, efi_guid_t *guid);

       int efi_guid_to_name(efi_guid_t *guid, char **name);

       int efi_guid_to_id_guid(efi_guid_t *guid, char **id_guid);

       int efi_guid_to_symbol(efi_guid_t *guid, char **symbol);
       int efi_symbol_to_guid(const char *symbol, efi_guid_t *guid);

DESCRIPTION

       efi_variables_supported() tests if the UEFI variable facility is supported on the current machine.

       efi_del_variable() deletes the variable specified by guid and name.

       efi_get_variable() gets the variable specified by guid and name. The value is stored in data, its size in
       data_size, and its attributes are stored in attributes.

       efi_get_variable_attributes() gets attributes for the variable specified by guid and name.

       efi_get_variable_size() gets the size of the data for the variable specified by guid and name.

       efi_append_variable() appends data of size size to the variable specified by guid and name.

       efi_set_variable()  sets  the  variable  specified  by  guid and name.  If the optional mode parameter is
       given, it will use those permissions to create the file, subject to umask.

       efi_get_next_variable_name() iterates across the currently extant variables,  passing  back  a  guid  and
       name.

       efi_str_to_guid() parses a UEFI GUID from string form to an efi_guid_t the caller provides

       efi_guid_to_str()  Creates a string representation of a UEFI GUID.  If sp is NULL, it returns how big the
       string would be.  If sp is not NULL but *sp is NULL, it allocates a string and returns it  with.   It  is
       the   caller's  responsibility  to  free  this  string.   If  sp  is  not  NULL  and  *sp  is  not  NULL,
       efi_guid_to_str() assumes there is an allocation of suitable size and uses it.

       efi_name_to_guid() translates from a well known name to an efi_guid_t the caller provides.

       efi_guid_to_name() translates from an efi_guid_t to a well known name.  If the  supplied  GUID  does  not
       have a well known name, this function is equivalent to efi_guid_to_str().

       efi_guid_to_id_guid()  translates  from  an  efi_guid_t to an {ID GUID}.  If the supplied GUID has a well
       known name, the {ID GUID} will  be  of  the  form  "{name_here}".   If  not,  it  will  be  of  the  form
       "{66b2af1c-6211-4082-95cb-9f73a4795a7e}".

       efi_id_guid_to_guid() translates from an {ID GUID} to an efi_guid_t the caller provides.

       efi_guid_to_symbol()  translates  from  an efi_guid_t to a unique (within libefivar) C-sytle symbol name.
       These symbol names are useful for printing as a unique, easily parsed identifier, and are also provide by
       the library and its header files.

       efi_symbol_to_guid()  translates  from  a libefivar efi_guid_$FOO symbol name to an efi_guid_t the caller
       provides.

RETURN VALUE

       efi_variables_supported() returns true if variables are supported on the running hardware, and  false  if
       they are not.

       efi_get_next_variable_name()  returns 0 when iteration has completed, 1 when iteration has not completed,
       and -1 on error.  In the event of an error, errno(3) is set appropriately.

       efi_del_variable(),    efi_get_variable(),    efi_get_variable_attributes(),     efi_get_variable_size(),
       efi_append_variable(),  efi_set_variable(), efi_str_to_guid(), efi_guid_to_str(), efi_name_to_guid(), and
       efi_guid_to_name() return negative on error and zero on success.

AUTHORS

       Peter Jones <pjones@redhat.com>

                                                 Thu Aug 20 2012                             EFI_GET_VARIABLE(3)