This file is indexed.

/usr/share/X11/xkb/symbols/level3 is in xkb-data 2.16-1ubuntu1.

This file is owned by root:root, with mode 0o644.

The actual contents of the file can be viewed below.

  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
// These partial variants assign ISO_Level3_Shift to various XKB keycodes
// so that the third shift level can be reached.

// The default behaviour:
// the right Alt key (AltGr) chooses the third symbol engraved on a key.
default  partial modifier_keys
xkb_symbols "ralt_switch" {
  key <RALT> {
    type[Group1]="ONE_LEVEL",
    symbols[Group1] = [ ISO_Level3_Shift ]
  };
  include "level3(modifier_mapping)"
};

// Ensure a mapping to a real modifier for LevelThree.
partial modifier_keys
xkb_symbols "modifier_mapping" {
  replace key <LVL3> {
    type[Group1] = "ONE_LEVEL",
    symbols[Group1] = [ ISO_Level3_Shift ]
  };
  modifier_map Mod5 { <LVL3> };
};

// The right Alt key never chooses the third level.
// This option attempts to undo the effect of a layout's inclusion of
// 'ralt_switch'.  You may want to also select another level3 option
// to map the level3 shift to some other key.
partial modifier_keys
xkb_symbols "ralt_alt" {
  key <RALT> {
    type[Group1]="TWO_LEVEL",
    type[Group2]="TWO_LEVEL",
    type[Group3]="TWO_LEVEL",
    type[Group4]="TWO_LEVEL",
    symbols[Group1] = [ Alt_R, Meta_R ],
    symbols[Group2] = [ Alt_R, Meta_R ],
    symbols[Group3] = [ Alt_R, Meta_R ],
    symbols[Group4] = [ Alt_R, Meta_R ]
  };
  modifier_map Mod1 { <RALT> };
};

// The right Alt key (while pressed) chooses the third shift level,
// and Compose is mapped to its second level.
partial modifier_keys
xkb_symbols "ralt_switch_multikey" {
  key <RALT> {
    type[Group1]="TWO_LEVEL",
    symbols[Group1] = [ ISO_Level3_Shift, Multi_key ]
  };
  include "level3(modifier_mapping)"
};

// A special case of the right-Alt switch -- for use with grp:alts_toggle.
hidden partial modifier_keys
xkb_symbols "ralt_switch_for_alts_toggle" {
  virtual_modifiers LAlt, AltGr;
  key <LALT> {
    type[Group1]="PC_RALT_LEVEL2",
    symbols[Group1] = [ Alt_L, ISO_Prev_Group, ISO_Prev_Group ],
    virtualMods= LAlt
  };
  key <RALT> {
    type[Group1]="PC_ALT_LEVEL2",
    symbols[Group1] = [ ISO_Level3_Shift, ISO_Next_Group ],
    virtualMods= AltGr
  };
  include "level3(modifier_mapping)"
};

// Either Alt key (while pressed) chooses the third shift level.
// (To be used mostly to imitate Mac OS functionality.)
partial modifier_keys
xkb_symbols "alt_switch" {
  include "level3(lalt_switch)"
  include "level3(ralt_switch)"
};

// The left Alt key (while pressed) chooses the third shift level.
partial modifier_keys
xkb_symbols "lalt_switch" {
  key <LALT> {
    type[Group1]="ONE_LEVEL",
    symbols[Group1] = [ ISO_Level3_Shift ]
  };
  include "level3(modifier_mapping)"
};

// The right Ctrl key (while pressed) chooses the third shift level.
partial modifier_keys
xkb_symbols "switch" {
  key <RCTL> {
    type[Group1]="ONE_LEVEL",
    symbols[Group1] = [ ISO_Level3_Shift ]
  };
  include "level3(modifier_mapping)"
};

// The Menu key (while pressed) chooses the third shift level.
partial modifier_keys
xkb_symbols "menu_switch" {
  key <MENU> {
    type[Group1]="ONE_LEVEL",
    symbols[Group1] = [ ISO_Level3_Shift ]
  };
  include "level3(modifier_mapping)"
};

// Either Win key (while pressed) chooses the third shift level.
partial modifier_keys
xkb_symbols "win_switch" {
  include "level3(lwin_switch)"
  include "level3(rwin_switch)"
};

// The left Win key (while pressed) chooses the third shift level.
partial modifier_keys
xkb_symbols "lwin_switch" {
  key <LWIN> {
    type[Group1]="ONE_LEVEL",
    symbols[Group1] = [ ISO_Level3_Shift ]
  };
  include "level3(modifier_mapping)"
};

// The right Win key (while pressed) chooses the third shift level.
// (When using this map, you should set your keyboard as pc101 or pc102
// instead of pc104 or pc105.)
partial modifier_keys
xkb_symbols "rwin_switch" {
  key <RWIN> {
    type[Group1]="ONE_LEVEL",
    symbols[Group1] = [ ISO_Level3_Shift ]
  };
  include "level3(modifier_mapping)"
};

// The Enter key on the kepypad (while pressed) chooses the third shift level.
// (This is especially useful for Mac laptops which miss the right Alt key.)
partial modifier_keys
xkb_symbols "enter_switch" {
  key <KPEN> {
    type[Group1]="ONE_LEVEL",
    symbols[Group1] = [ ISO_Level3_Shift ]
  };
  include "level3(modifier_mapping)"
};

// The CapsLock key (while pressed) chooses the third shift level.
partial modifier_keys
xkb_symbols "caps_switch" {
  key <CAPS> {
    type[Group1]="ONE_LEVEL",
    symbols[Group1] = [ ISO_Level3_Shift ]
  };
  include "level3(modifier_mapping)"
};

// The Backslash key (while pressed) chooses the third shift level.
partial modifier_keys
xkb_symbols "bksl_switch" {
  key <BKSL> {
    type[Group1]="ONE_LEVEL",
    symbols[Group1] = [ ISO_Level3_Shift ]
  };
  include "level3(modifier_mapping)"
};

// The Less/Greater key (while pressed) chooses the third shift level.
partial modifier_keys
xkb_symbols "lsgt_switch" {
  key <LSGT> {
    type[Group1]="ONE_LEVEL",
    symbols[Group1] = [ ISO_Level3_Shift ]
  };
  include "level3(modifier_mapping)"
};

// The CapsLock key (while pressed) chooses the third shift level,
// and latches when pressed together with another third-level chooser.
partial modifier_keys
xkb_symbols "caps_switch_latch" {
  key <CAPS> {
    type[Group1]="THREE_LEVEL",
    symbols[Group1] = [ ISO_Level3_Shift, ISO_Level3_Shift, ISO_Level3_Latch ]
  };
  include "level3(modifier_mapping)"
};

// The Backslash key (while pressed) chooses the third shift level,
// and latches when pressed together with another third-level chooser.
partial modifier_keys
xkb_symbols "bksl_switch_latch" {
  key <BKSL> {
    type[Group1]="THREE_LEVEL",
    symbols[Group1] = [ ISO_Level3_Shift, ISO_Level3_Shift, ISO_Level3_Latch ]
  };
  include "level3(modifier_mapping)"
};

// The Less/Greater key (while pressed) chooses the third shift level,
// and latches when pressed together with another third-level chooser.
partial modifier_keys
xkb_symbols "lsgt_switch_latch" {
  key <LSGT> {
    type[Group1]="THREE_LEVEL",
    symbols[Group1] = [ ISO_Level3_Shift, ISO_Level3_Shift, ISO_Level3_Latch ]
  };
  include "level3(modifier_mapping)"
};