EFI Shell2.0 commands -- setvar(改變一個UEFI變數值)

Changes the value of a UEFI variable.

setvar variable-name [–guid guid][-bs][-rs][-nv] [=data]

Options:

variable-name  The name of the UEFI variable to modify or display.

-guid                Specifies the GUID of the UEFI variable to modify or display. If not present, then the GUID EFI_GLOBAL_VARIABLE, as defined in chapter 3.2 of the UEFI specification.

-bs                    Indicates that the variable is a boot variable. Should only be present for new variables, otherwise it is ignored.

-rt                     Indicates that the variable is a runtime variable. Should only be present for new variables, otherwise it is ignored.

-nv                    Indicates that the variable is non-volatile. If not present, then the variable is assumed to be volatile. Should only be present for new variables, otherwise it is ignored.

=data                 New data for the variable. If there is nothing after the ‘=’ then the variable is deleted. If = is not present, then the current value of the variable is dumped as hex bytes. The data may consist of zero or more of the following:

xx[xx]:         Hexadecimal bytes

"ascii-string"  ASCII-string with no null-terminator

L"UCS2-string"  UCS-2 encoded string with no null-terminator

--device        Device path text format, as specified by the EFI Device Path Display Format Overview section of the UEFI Specification.

Description:

This command changes the UEFI variable specified by name and guid. If = is specified, but data is not, the variable is deleted, if it exists. If = is not specified, then the current variable contents are displayed. If =data is specified, then the variable’s value is changed to the value specified by data.

-bs, -rt and –nv are only useful if the variable already exists. If the variable already exists and the attributes cannot be changed, then -1 is returned.

Return Value:

• SHELL_SUCCESS          The shell has stored the variable and its data with the defined attributes.\r\n"
• SHELL_INVALID_PARAMETER Incorrect attributes were used.
• SHELL_OUT_OF_RESOURCES  Insufficient resources were available for storing the variable and its data.
• SHELL_DEVICE_ERROR The   variable could not be saved due to a hardware error.
• SHELL_WRITE_PROTECTED  The variable in question is read-only.
• SHELL_WRITE_PROTECTED  The variable in question cannot be deleted.
• SHELL_NOT_FOUND        The variable could not be found.