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_exists(efi_guid_t guid, const char *name);

       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, 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_exists() gets if the variable specified by guid and name exists.

       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, and sets the file mode to mode, subject
       to umask.  Note that the mode will not persist across a reboot, and that the permissions only apply if on
       systems using efivarfs.

       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-style  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_exists(),
       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)