Manpages - efi_get_variable.3

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

  #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);

*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-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.

*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.

  Peter Jones <pjones@redhat.com>