revisions.txt: mark optional rev arguments with []
[git/git.git] / Documentation / revisions.txt
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1SPECIFYING REVISIONS
2--------------------
3
61e508d9 4A revision parameter '<rev>' typically, but not necessarily, names a
d5fa1f1a 5commit object. It uses what is called an 'extended SHA-1'
5a8f3117 6syntax. Here are various ways to spell object names. The
b62c7697 7ones listed near the end of this list name trees and
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8blobs contained in a commit.
9
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10NOTE: This document shows the "raw" syntax as seen by git. The shell
11and other UIs might require additional quoting to protect special
12characters and to avoid word splitting.
13
61e508d9 14'<sha1>', e.g. 'dae86e1950b1277e545cee180551750029cfe735', 'dae86e'::
d5fa1f1a 15 The full SHA-1 object name (40-byte hexadecimal string), or
b62c7697 16 a leading substring that is unique within the repository.
5a8f3117 17 E.g. dae86e1950b1277e545cee180551750029cfe735 and dae86e both
b62c7697 18 name the same commit object if there is no other object in
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19 your repository whose object name starts with dae86e.
20
61e508d9 21'<describeOutput>', e.g. 'v1.7.4.2-679-g3bee7fb'::
b62c7697 22 Output from `git describe`; i.e. a closest tag, optionally
5a8f3117 23 followed by a dash and a number of commits, followed by a dash, a
83456b13 24 'g', and an abbreviated object name.
5a8f3117 25
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26'<refname>', e.g. 'master', 'heads/master', 'refs/heads/master'::
27 A symbolic ref name. E.g. 'master' typically means the commit
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28 object referenced by 'refs/heads/master'. If you
29 happen to have both 'heads/master' and 'tags/master', you can
2de9b711 30 explicitly say 'heads/master' to tell Git which one you mean.
89ce391b 31 When ambiguous, a '<refname>' is disambiguated by taking the
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32 first match in the following rules:
33
89ce391b 34 . If '$GIT_DIR/<refname>' exists, that is what you mean (this is usually
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35 useful only for `HEAD`, `FETCH_HEAD`, `ORIG_HEAD`, `MERGE_HEAD`
36 and `CHERRY_PICK_HEAD`);
5a8f3117 37
89ce391b 38 . otherwise, 'refs/<refname>' if it exists;
5a8f3117 39
b62c7697 40 . otherwise, 'refs/tags/<refname>' if it exists;
5a8f3117 41
89ce391b 42 . otherwise, 'refs/heads/<refname>' if it exists;
5a8f3117 43
89ce391b 44 . otherwise, 'refs/remotes/<refname>' if it exists;
5a8f3117 45
89ce391b 46 . otherwise, 'refs/remotes/<refname>/HEAD' if it exists.
5a8f3117 47+
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48`HEAD` names the commit on which you based the changes in the working tree.
49`FETCH_HEAD` records the branch which you fetched from a remote repository
83456b13 50with your last `git fetch` invocation.
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51`ORIG_HEAD` is created by commands that move your `HEAD` in a drastic
52way, to record the position of the `HEAD` before their operation, so that
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53you can easily change the tip of the branch back to the state before you ran
54them.
661c3e9b 55`MERGE_HEAD` records the commit(s) which you are merging into your branch
83456b13 56when you run `git merge`.
661c3e9b 57`CHERRY_PICK_HEAD` records the commit which you are cherry-picking
83456b13 58when you run `git cherry-pick`.
5a8f3117 59+
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60Note that any of the 'refs/*' cases above may come either from
61the '$GIT_DIR/refs' directory or from the '$GIT_DIR/packed-refs' file.
e1c3bf49 62While the ref name encoding is unspecified, UTF-8 is preferred as
1452bd64 63some output processing may assume ref names in UTF-8.
5a8f3117 64
9ba89f48 65'@'::
661c3e9b 66 '@' alone is a shortcut for `HEAD`.
9ba89f48 67
d86d2074 68'[<refname>]@{<date>}', e.g. 'master@\{yesterday\}', 'HEAD@{5 minutes ago}'::
61e508d9 69 A ref followed by the suffix '@' with a date specification
5a8f3117 70 enclosed in a brace
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71 pair (e.g. '\{yesterday\}', '{1 month 2 weeks 3 days 1 hour 1
72 second ago}' or '{1979-02-26 18:30:00}') specifies the value
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73 of the ref at a prior point in time. This suffix may only be
74 used immediately following a ref name and the ref must have an
83456b13 75 existing log ('$GIT_DIR/logs/<ref>'). Note that this looks up the state
5a8f3117 76 of your *local* ref at a given time; e.g., what was in your local
83456b13 77 'master' branch last week. If you want to look at commits made during
bcf9626a 78 certain times, see `--since` and `--until`.
5a8f3117 79
c200deb8 80'<refname>@{<n>}', e.g. 'master@\{1\}'::
61e508d9 81 A ref followed by the suffix '@' with an ordinal specification
b62c7697 82 enclosed in a brace pair (e.g. '\{1\}', '\{15\}') specifies
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83 the n-th prior value of that ref. For example 'master@\{1\}'
84 is the immediate prior value of 'master' while 'master@\{5\}'
85 is the 5th prior value of 'master'. This suffix may only be used
86 immediately following a ref name and the ref must have an existing
61e508d9 87 log ('$GIT_DIR/logs/<refname>').
5a8f3117 88
c200deb8 89'@{<n>}', e.g. '@\{1\}'::
61e508d9 90 You can use the '@' construct with an empty ref part to get at a
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91 reflog entry of the current branch. For example, if you are on
92 branch 'blabla' then '@\{1\}' means the same as 'blabla@\{1\}'.
5a8f3117 93
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94'@{-<n>}', e.g. '@{-1}'::
95 The construct '@{-<n>}' means the <n>th branch/commit checked out
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96 before the current one.
97
d86d2074 98'[<branchname>]@\{upstream\}', e.g. 'master@\{upstream\}', '@\{u\}'::
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99 The suffix '@\{upstream\}' to a branchname (short form '<branchname>@\{u\}')
100 refers to the branch that the branch specified by branchname is set to build on
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101 top of (configured with `branch.<name>.remote` and
102 `branch.<name>.merge`). A missing branchname defaults to the
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103 current one. These suffixes are also accepted when spelled in uppercase, and
104 they mean the same thing no matter the case.
5a8f3117 105
d86d2074 106'[<branchname>]@\{push\}', e.g. 'master@\{push\}', '@\{push\}'::
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107 The suffix '@\{push}' reports the branch "where we would push to" if
108 `git push` were run while `branchname` was checked out (or the current
661c3e9b 109 `HEAD` if no branchname is specified). Since our push destination is
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110 in a remote repository, of course, we report the local tracking branch
111 that corresponds to that branch (i.e., something in 'refs/remotes/').
112+
113Here's an example to make it more clear:
114+
115------------------------------
116$ git config push.default current
117$ git config remote.pushdefault myfork
118$ git checkout -b mybranch origin/master
119
120$ git rev-parse --symbolic-full-name @{upstream}
121refs/remotes/origin/master
122
123$ git rev-parse --symbolic-full-name @{push}
124refs/remotes/myfork/mybranch
125------------------------------
126+
127Note in the example that we set up a triangular workflow, where we pull
128from one location and push to another. In a non-triangular workflow,
129'@\{push}' is the same as '@\{upstream}', and there is no need for it.
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130+
131This suffix is also accepted when spelled in uppercase, and means the same
132thing no matter the case.
adfe5d04 133
d86d2074 134'<rev>{caret}[<n>]', e.g. 'HEAD{caret}, v1.5.1{caret}0'::
61e508d9 135 A suffix '{caret}' to a revision parameter means the first parent of
5a8f3117 136 that commit object. '{caret}<n>' means the <n>th parent (i.e.
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137 '<rev>{caret}'
138 is equivalent to '<rev>{caret}1'). As a special rule,
139 '<rev>{caret}0' means the commit itself and is used when '<rev>' is the
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140 object name of a tag object that refers to a commit object.
141
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142'<rev>{tilde}<n>', e.g. 'master{tilde}3'::
143 A suffix '{tilde}<n>' to a revision parameter means the commit
70eb1307 144 object that is the <n>th generation ancestor of the named
b62c7697 145 commit object, following only the first parents. I.e. '<rev>{tilde}3' is
61e508d9 146 equivalent to '<rev>{caret}{caret}{caret}' which is equivalent to
b62c7697 147 '<rev>{caret}1{caret}1{caret}1'. See below for an illustration of
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148 the usage of this form.
149
c200deb8 150'<rev>{caret}{<type>}', e.g. 'v0.99.8{caret}\{commit\}'::
61e508d9 151 A suffix '{caret}' followed by an object type name enclosed in
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152 brace pair means dereference the object at '<rev>' recursively until
153 an object of type '<type>' is found or the object cannot be
154 dereferenced anymore (in which case, barf).
155 For example, if '<rev>' is a commit-ish, '<rev>{caret}\{commit\}'
156 describes the corresponding commit object.
157 Similarly, if '<rev>' is a tree-ish, '<rev>{caret}\{tree\}'
158 describes the corresponding tree object.
159 '<rev>{caret}0'
b62c7697 160 is a short-hand for '<rev>{caret}\{commit\}'.
a6a3f2cc 161+
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162'<rev>{caret}\{object\}' can be used to make sure '<rev>' names an
163object that exists, without requiring '<rev>' to be a tag, and
164without dereferencing '<rev>'; because a tag is already an object,
a6a3f2cc 165it does not have to be dereferenced even once to get to an object.
75aa26d3 166+
e277ff43 167'<rev>{caret}\{tag\}' can be used to ensure that '<rev>' identifies an
75aa26d3 168existing tag object.
5a8f3117 169
c200deb8 170'<rev>{caret}{}', e.g. 'v0.99.8{caret}{}'::
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171 A suffix '{caret}' followed by an empty brace pair
172 means the object could be a tag,
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173 and dereference the tag recursively until a non-tag object is
174 found.
175
c200deb8 176'<rev>{caret}{/<text>}', e.g. 'HEAD^{/fix nasty bug}'::
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177 A suffix '{caret}' to a revision parameter, followed by a brace
178 pair that contains a text led by a slash,
b62c7697 179 is the same as the ':/fix nasty bug' syntax below except that
32574b68 180 it returns the youngest matching commit which is reachable from
61e508d9 181 the '<rev>' before '{caret}'.
32574b68 182
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183':/<text>', e.g. ':/fix nasty bug'::
184 A colon, followed by a slash, followed by a text, names
95ad6d2d 185 a commit whose commit message matches the specified regular expression.
5a8f3117 186 This name returns the youngest matching commit which is
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187 reachable from any ref. The regular expression can match any part of the
188 commit message. To match messages starting with a string, one can use
189 e.g. ':/^foo'. The special sequence ':/!' is reserved for modifiers to what
190 is matched. ':/!-foo' performs a negative match, while ':/!!foo' matches a
191 literal '!' character, followed by 'foo'. Any other sequence beginning with
192 ':/!' is reserved for now.
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193 Depending on the given text, the shell's word splitting rules might
194 require additional quoting.
5a8f3117 195
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196'<rev>:<path>', e.g. 'HEAD:README', ':README', 'master:./README'::
197 A suffix ':' followed by a path names the blob or tree
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198 at the given path in the tree-ish object named by the part
199 before the colon.
61e508d9 200 ':path' (with an empty part before the colon)
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201 is a special case of the syntax described next: content
202 recorded in the index at the given path.
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203 A path starting with './' or '../' is relative to the current working directory.
204 The given path will be converted to be relative to the working tree's root directory.
979f7929 205 This is most useful to address a blob or tree from a commit or tree that has
b62c7697 206 the same tree structure as the working tree.
5a8f3117 207
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208':<n>:<path>', e.g. ':0:README', ':README'::
209 A colon, optionally followed by a stage number (0 to 3) and a
210 colon, followed by a path, names a blob object in the
b62c7697 211 index at the given path. A missing stage number (and the colon
61e508d9 212 that follows it) names a stage 0 entry. During a merge, stage
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213 1 is the common ancestor, stage 2 is the target branch's version
214 (typically the current branch), and stage 3 is the version from
b62c7697 215 the branch which is being merged.
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216
217Here is an illustration, by Jon Loeliger. Both commit nodes B
218and C are parents of commit node A. Parent commits are ordered
219left-to-right.
220
221........................................
222G H I J
223 \ / \ /
224 D E F
225 \ | / \
226 \ | / |
227 \|/ |
228 B C
229 \ /
230 \ /
231 A
232........................................
233
234 A = = A^0
235 B = A^ = A^1 = A~1
236 C = A^2 = A^2
237 D = A^^ = A^1^1 = A~2
238 E = B^2 = A^^2
239 F = B^3 = A^^3
240 G = A^^^ = A^1^1^1 = A~3
241 H = D^2 = B^^2 = A^^^2 = A~2^2
242 I = F^ = B^3^ = A^^3^
243 J = F^2 = B^3^2 = A^^3^2
244
245
246SPECIFYING RANGES
247-----------------
248
83456b13 249History traversing commands such as `git log` operate on a set
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250of commits, not just a single commit.
251
252For these commands,
253specifying a single revision, using the notation described in the
254previous section, means the set of commits `reachable` from the given
255commit.
256
257A commit's reachable set is the commit itself and the commits in
258its ancestry chain.
259
5a8f3117 260
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261Commit Exclusions
262~~~~~~~~~~~~~~~~~
263
264'{caret}<rev>' (caret) Notation::
265 To exclude commits reachable from a commit, a prefix '{caret}'
266 notation is used. E.g. '{caret}r1 r2' means commits reachable
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267 from 'r2' but exclude the ones reachable from 'r1' (i.e. 'r1' and
268 its ancestors).
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269
270Dotted Range Notations
271~~~~~~~~~~~~~~~~~~~~~~
272
273The '..' (two-dot) Range Notation::
274 The '{caret}r1 r2' set operation appears so often that there is a shorthand
275 for it. When you have two commits 'r1' and 'r2' (named according
276 to the syntax explained in SPECIFYING REVISIONS above), you can ask
277 for commits that are reachable from r2 excluding those that are reachable
278 from r1 by '{caret}r1 r2' and it can be written as 'r1..r2'.
279
9fe92388 280The '...' (three-dot) Symmetric Difference Notation::
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281 A similar notation 'r1\...r2' is called symmetric difference
282 of 'r1' and 'r2' and is defined as
283 'r1 r2 --not $(git merge-base --all r1 r2)'.
284 It is the set of commits that are reachable from either one of
285 'r1' (left side) or 'r2' (right side) but not from both.
286
287In these two shorthand notations, you can omit one end and let it default to HEAD.
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288For example, 'origin..' is a shorthand for 'origin..HEAD' and asks "What
289did I do since I forked from the origin branch?" Similarly, '..origin'
290is a shorthand for 'HEAD..origin' and asks "What did the origin do since
291I forked from them?" Note that '..' would mean 'HEAD..HEAD' which is an
292empty range that is both reachable and unreachable from HEAD.
293
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294Other <rev>{caret} Parent Shorthand Notations
295~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
8779351d 296Three other shorthands exist, particularly useful for merge commits,
391a3c70 297for naming a set that is formed by a commit and its parent commits.
5a8f3117 298
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299The 'r1{caret}@' notation means all parents of 'r1'.
300
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301The 'r1{caret}!' notation includes commit 'r1' but excludes all of its parents.
302By itself, this notation denotes the single commit 'r1'.
391a3c70 303
d86d2074 304The '<rev>{caret}-[<n>]' notation includes '<rev>' but excludes the <n>th
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305parent (i.e. a shorthand for '<rev>{caret}<n>..<rev>'), with '<n>' = 1 if
306not given. This is typically useful for merge commits where you
307can just pass '<commit>{caret}-' to get all the commits in the branch
308that was merged in merge commit '<commit>' (including '<commit>'
309itself).
310
39b4d85e 311While '<rev>{caret}<n>' was about specifying a single commit parent, these
8779351d 312three notations also consider its parents. For example you can say
39b4d85e 313'HEAD{caret}2{caret}@', however you cannot say 'HEAD{caret}@{caret}2'.
5a8f3117 314
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315Revision Range Summary
316----------------------
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317
318'<rev>'::
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319 Include commits that are reachable from <rev> (i.e. <rev> and its
320 ancestors).
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321
322'{caret}<rev>'::
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323 Exclude commits that are reachable from <rev> (i.e. <rev> and its
324 ancestors).
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325
326'<rev1>..<rev2>'::
327 Include commits that are reachable from <rev2> but exclude
3a4dc486 328 those that are reachable from <rev1>. When either <rev1> or
661c3e9b 329 <rev2> is omitted, it defaults to `HEAD`.
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330
331'<rev1>\...<rev2>'::
332 Include commits that are reachable from either <rev1> or
3a4dc486 333 <rev2> but exclude those that are reachable from both. When
661c3e9b 334 either <rev1> or <rev2> is omitted, it defaults to `HEAD`.
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335
336'<rev>{caret}@', e.g. 'HEAD{caret}@'::
337 A suffix '{caret}' followed by an at sign is the same as listing
338 all parents of '<rev>' (meaning, include anything reachable from
339 its parents, but not the commit itself).
340
341'<rev>{caret}!', e.g. 'HEAD{caret}!'::
342 A suffix '{caret}' followed by an exclamation mark is the same
343 as giving commit '<rev>' and then all its parents prefixed with
344 '{caret}' to exclude them (and their ancestors).
345
733e064d 346'<rev>{caret}-<n>', e.g. 'HEAD{caret}-, HEAD{caret}-2'::
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347 Equivalent to '<rev>{caret}<n>..<rev>', with '<n>' = 1 if not
348 given.
349
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350Here are a handful of examples using the Loeliger illustration above,
351with each step in the notation's expansion and selection carefully
352spelt out:
5a8f3117 353
37980505 354....
7a5370e6 355 Args Expanded arguments Selected commits
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356 D G H D
357 D F G H I J D F
358 ^G D H D
359 ^D B E I J F B
360 ^D B C E I J F B C
361 C I J F C
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362 B..C = ^B C C
363 B...C = B ^F C G H D E B C
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364 B^- = B^..B
365 = ^B^1 B E I J F B
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366 C^@ = C^1
367 = F I J F
368 B^@ = B^1 B^2 B^3
369 = D E F D G H E F I J
370 C^! = C ^C^@
371 = C ^C^1
372 = C ^F C
373 B^! = B ^B^@
374 = B ^B^1 ^B^2 ^B^3
375 = B ^D ^E ^F B
376 F^! D = F ^I ^J D G H D F
37980505 377....