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32 .Nd UEFI environemnt variable interaction
44 .Op Fl -fromfile Ar file
57 .Dq Unified Extensible Firmware Interface
59 environment variables.
60 UEFI variables have three part: A namespace, a name and a value.
61 The namespace is a GUID that's self assigned by the group defining the
63 The name is a Unicode name for the variable.
64 The value is binary data.
65 All Unicode data is presented to the user as UTF-8.
67 The following options are available:
69 .It Fl n Ar name Fl -name Ar name
70 Specify the name of the variable to operate on.
73 argument is the GUID of variable, followed by a dash, followed by the
75 The GUID may be in numeric format, or may be one of the well known
79 .It Fl f Ar file Fl -fromfile Ar file
80 When writing or appending to a variable, take the data for the
83 instead of from the command line.
89 This is not well understood and currently unimplemented.
91 Append the specified value to the UEFI variable rather than replacing
93 .It Fl t Ar attr Fl -attributes Ar attr
94 Specify, in user hostile hexidecimal, the attributes for this
96 See section 7.2 (GetVariable subsection, Related Definitions) of the
97 UEFI Specification for hex values to use.
99 Display the variable data as modified ascii: All printable characters
100 are printed, while unprintable characters are rendered as a two-digit
101 hexadecimal number preceeded by a % character.
103 Display the variable data as binary data.
104 Usually will be used with the
111 Delete the specified variable.
112 May not be used with either the
120 .It Fl d Fl -device Fl -device-path
121 Interpret the variables printed as UEFI device paths and print the
122 UEFI standard string representation.
124 flag is specified, guids are converted to names if they are known (and
128 List variable data as a hex dump.
129 .It Fl L Fl -list-guids
130 Lists the well known GUIDs.
131 The names listed here may be used in place of the numeric GUID values.
132 These names will replace the numeric GUID values unless
136 List all the variables.
139 flag is also listed, their values will be displayed.
141 Do not display the variable name.
143 Print the value of the variable.
144 .It Fl R Fl -raw-guid
145 Do not substitute well known names for GUID numeric values in output.
147 Write (replace) the variable specified with the value specified from
149 No command line option to do this is available since UEFI variables
150 are binary structures rather than strings.
153 can be used to specify simple strings.
157 environment variable.
161 program is intended to be compatible (strict superset) with a progam
162 of the same name included in the Red Hat libefivar package.
168 flags are not implmenented and never will be.
171 flag is a short-hand for
174 Appendix A of the UEFI specification has the format for GUIDs.
176 .Dq Globally Unique Identifiers
177 have the format described in RFC 4122.
184 utility first appeared in