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GNU Find Flashcards: Expressions, Output & Pruning

Predict GNU find output, repair expression grouping and missing prints, and distinguish filtering from directory pruning with 40 short tree-based exercises.

作者 Open Study Contributor

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Practice GNU find expressions with 40 short, original exercises. Read a complete directory tree and command, predict the printed set, explain a missing result or an unexpected directory, or make a restricted repair. The examples separate expression truth, output actions, and directory descent. All fixtures use regular files and directories; output order is irrelevant.

The cards practice tree + command → output or branch explanation, faulty expression + stated goal → one constrained repair, and two commands with equal output → the difference in visited descendants. They move from name/path matching, shell quoting and implicit AND into precedence, grouping, negation and short-circuit printing, then pruning and mixed diagnosis. Closely related variants are separated by at least three other cards. Arbitrary output → command reversal and exhaustive equivalent rewrites are excluded because they do not give a single useful answer.

Scope: -name, -path, -type f/d, implicit/explicit AND, OR, negation, grouping, explicit/default -print, -prune, and one -depth caution showing why children-before-directory traversal defeats pruning. It is not a complete find course. Time, size and permission filters, depth-limit calculations, deletion, command execution, filename transport, symlinks, filesystem races and BSD/macOS portability are outside this deck.

The original trees, questions, answers and order were created with AI assistance. All 40 original fixtures and seven comparison or repair commands were checked with GNU findutils 4.10.0, both directly and through /bin/sh; visited-entry instrumentation checked traversal claims. Behavior facts were checked against the GNU find manual page and the manual included in the GNU findutils 4.10.0 release source. No manual prose, source code, competitor cards or third-party illustrations were copied. The cover is an original AI-generated illustration. CC0 1.0 applies to the original deck text, organization, metadata and cover to the extent applicable rights exist; factual behavior is not owned, and GNU documentation and source retain their own licenses.

An independent, unofficial learning resource with no affiliation with or endorsement by GNU or the Free Software Foundation.

这套卡组中的卡片

  1. 卡片 1

    问题

    GNU find; run from this complete tree's parent. Trailing / marks directories; other entries are regular files. Ignore output order.

    atlas/
atlas/draft/
atlas/draft/seed.txt
atlas/seed.txt

    find atlas -name 'draft/seed.txt'

    Which paths print?

    答案

    None. -name tests the final name component, so a pattern containing / cannot match these names.

  2. 卡片 2

    问题

    GNU find; run from this complete tree's parent. Trailing / marks directories; other entries are regular files. Ignore output order.

    bay/
bay/card.md/
bay/card.md/inner
bay/page.md
bay/readme.txt

    find bay -type f -name '*.md'

    Which paths print?

    答案

    bay/page.md. Adjacent tests mean AND: the entry must be a regular file and have a name ending in .md.

  3. 卡片 3

    问题

    GNU find; run from this complete tree's parent. Trailing / marks directories; other entries are regular files. Ignore output order.

    cedar/
cedar/one.log
cedar/two.log
cedar/raw/
cedar/raw/three.log

    find cedar -name '*.log'

    Why keep the quotes around the pattern?

    答案

    They pass the literal pattern *.log to find instead of letting the shell expand it. All three .log files print, including cedar/raw/three.log.

  4. 卡片 4

    问题

    GNU find; run from this complete tree's parent. Trailing / marks directories; other entries are regular files. Ignore output order.

    dune/
dune/keep.txt
dune/skip.txt
dune/skip.txt.box/

    find dune -type f ! -name 'skip.txt'

    Which paths print?

    答案

    dune/keep.txt. ! negates the following name test; the regular-file guard still applies.

  5. 卡片 5

    问题

    GNU find; run from this complete tree's parent. Trailing / marks directories; other entries are regular files. Ignore output order.

    ember/
ember/first.c
ember/second.h
ember/cache.h/
ember/cache.h/chunk

    find ember -type f -name '*.c' -o -name '*.h'

    Which paths print?

    答案

    ember/first.c, ember/second.h, and directory ember/cache.h. AND binds more tightly than OR, so the .h branch has no regular-file guard.

  6. 卡片 6

    问题

    GNU find; run from this complete tree's parent. Trailing / marks directories; other entries are regular files. Ignore output order.

    fern/
fern/.note.md
fern/plain.md
fern/deep/
fern/deep/.other.md

    find fern -name '*.md'

    Which paths print?

    答案

    All three .md files. GNU find's -name pattern can match a leading dot; the shell receives the quoted pattern unchanged.

  7. 卡片 7

    问题

    GNU find; run from this complete tree's parent. Trailing / marks directories; other entries are regular files. Ignore output order.

    grove/
grove/pkg/
grove/pkg/part.txt
grove/part.txt

    find ./grove -path './grove/pkg/part.txt'

    Which paths print?

    答案

    ./grove/pkg/part.txt. -path matches the encountered path, including the starting point's ./ prefix.

  8. 卡片 8

    问题

    GNU find; run from this complete tree's parent. Trailing / marks directories; other entries are regular files. Ignore output order.

    harbor/
harbor/red.txt
harbor/blue.txt
harbor/green.txt

    find harbor \( -name 'red.txt' -o -name 'blue.txt' \)

    Why are the parentheses escaped?

    答案

    So the shell passes ( and ) as arguments to find for grouping. The printed set is harbor/red.txt and harbor/blue.txt.

  9. 卡片 9

    问题

    GNU find; run from this complete tree's parent. Trailing / marks directories; other entries are regular files. Ignore output order.

    iris/
iris/a.csv
iris/b.tsv
iris/c.txt

    find iris -name '*.csv' -o -name '*.tsv' -print

    Which paths print?

    答案

    iris/b.tsv only. A true .csv branch short-circuits OR before -print; the explicit action also disables default printing for the command.

  10. 卡片 10

    问题

    GNU find; run from this complete tree's parent. Trailing / marks directories; other entries are regular files. Ignore output order.

    juniper/
juniper/a.dat
juniper/b.txt
juniper/folder.dat/

    find juniper -type f -a -name '*.dat' -print

    If only -a is removed, does the printed set change?

    答案

    No. Both forms print only juniper/a.dat; an omitted operator between primaries means AND.

  11. 卡片 11

    问题

    GNU find; run from this complete tree's parent. Trailing / marks directories; other entries are regular files. Ignore output order.

    kestrel/
kestrel/a.py
kestrel/b.pyi
kestrel/stub.pyi/

    find kestrel -type f -name '*.py' -o -name '*.pyi'

    Add only grouping parentheses so both name alternatives require a regular file. Give the repaired command.

    答案

    find kestrel -type f \( -name '*.py' -o -name '*.pyi' \)

    This prints kestrel/a.py and kestrel/b.pyi. The type guard now applies to the whole name choice.

  12. 卡片 12

    问题

    GNU find; run from this complete tree's parent. Trailing / marks directories; other entries are regular files. Ignore output order.

    lagoon/
lagoon/start.txt
lagoon/end.txt
lagoon/other.txt

    find lagoon -name 'start.txt' -print -o -name 'end.txt'

    Does lagoon/end.txt print?

    答案

    No. The second branch is true for it, but that branch has no print action. An explicit -print anywhere in the expression disables default printing for the whole command.

  13. 卡片 13

    问题

    GNU find; run from this complete tree's parent. Trailing / marks directories; other entries are regular files. Ignore output order.

    maple/
maple/red.txt
maple/blue.txt
maple/gray.txt

    find maple -type f ! \( -name 'red.txt' -o -name 'blue.txt' \)

    Which paths print?

    答案

    maple/gray.txt. Negating the grouped OR excludes both named files.

  14. 卡片 14

    问题

    GNU find; run from this complete tree's parent. Trailing / marks directories; other entries are regular files. Ignore output order.

    nectar/
nectar/a.json
nectar/b.yaml
nectar/c.ini

    find nectar -name '*.json' -o -name '*.yaml' -print

    Add only parentheses so either filename branch reaches the final print. Give the repaired command.

    答案

    find nectar \( -name '*.json' -o -name '*.yaml' \) -print

    Both nectar/a.json and nectar/b.yaml print; the action is now after the grouped choice.

  15. 卡片 15

    问题

    GNU find; run from this complete tree's parent. Trailing / marks directories; other entries are regular files. Ignore output order.

    opal/
opal/release notes.txt
opal/release.txt
opal/notes.txt

    find opal -type f -name 'release notes.txt' -print

    Which paths print?

    答案

    opal/release notes.txt. The quotes make the space-bearing pattern one shell argument; the space is part of the filename.

  16. 卡片 16

    问题

    GNU find; run from this complete tree's parent. Trailing / marks directories; other entries are regular files. Ignore output order.

    pine/
pine/real.txt

    find pine -name 'absent.txt' -print

    With readable entries and no I/O errors, what are the output and exit status?

    答案

    No paths; exit status 0. A false selection expression is not a process error.

  17. 卡片 17

    问题

    GNU find; run from this complete tree's parent. Trailing / marks directories; other entries are regular files. Ignore output order.

    quartz/
quartz/hot.txt
quartz/cold.txt
quartz/mild.txt

    find quartz -type f \( ! -name 'hot.txt' -o ! -name 'cold.txt' \)

    Which paths print?

    答案

    All three regular files. Every name differs from at least one of the two distinct names; OR of these negatives excludes neither.

  18. 卡片 18

    问题

    GNU find; run from this complete tree's parent. Trailing / marks directories; other entries are regular files. Ignore output order.

    reed/
reed/pass.txt
reed/fail.bin

    find reed -print -name '*.txt'

    Which paths print?

    答案

    reed, reed/pass.txt, and reed/fail.bin. -print runs before the name test; a later false result cannot undo output.

  19. 卡片 19

    问题

    GNU find; run from this complete tree's parent. Trailing / marks directories; other entries are regular files. Ignore output order.

    sable/
sable/r.c
sable/s.h
sable/box.h/

    find sable \( -name '*.c' -o -name '*.h' \) -type f -print

    Which paths print, and does putting the type test after the group break the guard?

    答案

    sable/r.c and sable/s.h. It still works: the grouped name choice and the type test are joined by AND before printing.

  20. 卡片 20

    问题

    GNU find; run from this complete tree's parent. Trailing / marks directories; other entries are regular files. Ignore output order.

    tamarind/
tamarind/cache/
tamarind/cache/old.txt
tamarind/fresh.txt

    find tamarind -type d -name 'cache' -prune -o -type f -print

    Which paths print, and is cache/old.txt visited?

    答案

    Only tamarind/fresh.txt prints. The cache directory is encountered and pruned; its child is not visited. The true pruning branch skips the right side of OR.

  21. 卡片 21

    问题

    GNU find; run from this complete tree's parent. Trailing / marks directories; other entries are regular files. Ignore output order.

    umber/
umber/yes.txt
umber/no.txt

    find umber -name 'yes.txt' -o -name 'no.txt' -print

    For umber/yes.txt, is the full expression true, and does it print?

    答案

    The expression is true, but it does not print. The left branch succeeds and OR skips the branch containing the only output action.

  22. 卡片 22

    问题

    GNU find; run from this complete tree's parent. Trailing / marks directories; other entries are regular files. Ignore output order.

    violet/
violet/cache/
violet/cache/hidden.txt
violet/live.txt

    find violet -name 'cache' -prune -o -type f

    Which paths print?

    答案

    violet/cache and violet/live.txt. -prune alone does not disable default printing, and the full expression is true for the pruned directory. Its child is not visited.

  23. 卡片 23

    问题

    GNU find; run from this complete tree's parent. Trailing / marks directories; other entries are regular files. Ignore output order.

    willow/
willow/build/
willow/build/a.txt
willow/vendor/
willow/vendor/b.txt
willow/src/
willow/src/c.txt

    find willow -type d \( -name 'build' -o -name 'vendor' \) -prune -o -type f -print

    Which paths print?

    答案

    willow/src/c.txt only. Both directory names are inside the pruning branch, so neither excluded directory's descendants are visited.

  24. 卡片 24

    问题

    GNU find; run from this complete tree's parent. Trailing / marks directories; other entries are regular files. Ignore output order.

    xenia/
xenia/cache/
xenia/cache/a.txt
xenia/b.txt

    find xenia -type f ! -path 'xenia/cache/*' -print

    Does this prevent traversal into xenia/cache?

    答案

    No. It prints only xenia/b.txt, but still visits xenia/cache/a.txt. A path test filters output; it does not stop directory descent.

  25. 卡片 25

    问题

    GNU find; run from this complete tree's parent. Trailing / marks directories; other entries are regular files. Ignore output order.

    yarrow/
yarrow/cache/
yarrow/cache/a.txt
yarrow/src/
yarrow/src/cache/
yarrow/src/cache/b.txt
yarrow/c.txt

    find yarrow -path 'yarrow/cache' -prune -o -type f -print

    Which regular files print?

    答案

    yarrow/src/cache/b.txt and yarrow/c.txt. Only the exact encountered path yarrow/cache is pruned; the nested cache is a different path.

  26. 卡片 26

    问题

    GNU find; run from this complete tree's parent. Trailing / marks directories; other entries are regular files. Ignore output order.

    zinnia/
zinnia/cache/
zinnia/cache/a
zinnia/b

    find zinnia -type d -name 'cache' -prune -print

    Does the pruned directory print, and are its children visited?

    答案

    zinnia/cache prints; its child is not visited. -prune returns true, so AND continues to the explicit -print for that directory.

  27. 卡片 27

    问题

    GNU find; run from this complete tree's parent. Trailing / marks directories; other entries are regular files. Ignore output order.

    acorn/
acorn/cache
acorn/src/
acorn/src/cache/
acorn/src/cache/a
acorn/src/live

    find acorn -type d -name 'cache' -prune -o -type f -print

    Which paths print?

    答案

    acorn/cache and acorn/src/live. The type guard keeps the regular file named cache out of the pruning branch; the nested cache directory is pruned.

  28. 卡片 28

    问题

    GNU find; run from this complete tree's parent. Trailing / marks directories; other entries are regular files. Ignore output order.

    birch/
birch/build/
birch/build/a.txt
birch/vendor/
birch/vendor/b.txt
birch/c.txt

    find birch -name 'build' -o -name 'vendor' -prune -o -type f -print

    Which excluded directory still has its child visited and printed?

    答案

    birch/build: its a.txt child prints, along with birch/c.txt. Matching the first OR branch skips -prune; only the vendor branch reaches it.

  29. 卡片 29

    问题

    GNU find; run from this complete tree's parent. Trailing / marks directories; other entries are regular files. Ignore output order.

    cobalt/
cobalt/cache/
cobalt/cache/a.txt
cobalt/b.txt

    find cobalt -depth -name 'cache' -prune -o -type f -print

    Does pruning prevent the cache child's visit or output?

    答案

    No. Both cobalt/cache/a.txt and cobalt/b.txt print. -depth processes children before their directory, so pruning that directory comes too late.

  30. 卡片 30

    问题

    GNU find; run from this complete tree's parent. Trailing / marks directories; other entries are regular files. Ignore output order.

    drift/
drift/cache/
drift/cache/a.txt
drift/lib/
drift/lib/cache/
drift/lib/cache/b.txt
drift/c.txt

    find drift -type d -name 'cache' -prune -o -type f -print

    Which regular files print?

    答案

    drift/c.txt only. A directory-name test catches both the top-level cache and the nested one.

  31. 卡片 31

    问题

    GNU find; run from this complete tree's parent. Trailing / marks directories; other entries are regular files. Ignore output order.

    easel/
easel/a.txt
easel/sub/
easel/sub/b.txt

    find easel -name 'easel' -prune -o -type f -print

    Which paths print?

    答案

    None. The starting directory itself matches and is pruned, so none of its descendants are visited.

  32. 卡片 32

    问题

    GNU find; run from this complete tree's parent. Trailing / marks directories; other entries are regular files. Ignore output order.

    flint/
flint/cache/
flint/cache/a.txt
flint/b.txt

    find flint -type d -name 'cache' -prune -type f -print

    Why does even flint/b.txt fail to print?

    答案

    Every primary is joined by AND. Regular files fail -type d; the pruned cache directory fails -type f. No entry reaches -print.

  33. 卡片 33

    问题

    GNU find; run from this complete tree's parent. Trailing / marks directories; other entries are regular files. Ignore output order.

    garnet/
garnet/cache/
garnet/cache/a
garnet/b

    find garnet \( -name 'cache' -prune -o -type f \) -print

    Which paths print?

    答案

    garnet/cache and garnet/b. The final print applies to either successful branch, including the true pruning branch.

  34. 卡片 34

    问题

    GNU find; run from this complete tree's parent. Trailing / marks directories; other entries are regular files. Ignore output order.

    heath/
heath/cache/
heath/cache/a
heath/lib/
heath/lib/cache/
heath/lib/cache/b
heath/c

    find heath -path 'heath/cache' -prune -o -type f -print

    Replace only -path 'heath/cache' so every directory named cache is pruned, wherever nested. Give the replacement.

    答案

    -type d -name 'cache'. The repaired command prints only heath/c; it prunes both cache directories.

  35. 卡片 35

    问题

    GNU find; run from this complete tree's parent. Trailing / marks directories; other entries are regular files. Ignore output order.

    indigo/
indigo/.stash/
indigo/.stash/a.txt
indigo/.memo.txt
indigo/b.txt

    find indigo -type d -name '.stash' -prune -o -type f -name '*.txt' -print

    Which paths print?

    答案

    indigo/.memo.txt and indigo/b.txt. The hidden directory is pruned, while the quoted name pattern still matches the hidden regular file.

  36. 卡片 36

    问题

    GNU find; run from this complete tree's parent. Trailing / marks directories; other entries are regular files. Ignore output order.

    jasper/
jasper/build/
jasper/build/a
jasper/vendor/
jasper/vendor/b
jasper/c

    find jasper -name 'build' -o -name 'vendor' -prune -o -type f -print

    Add only parentheses so both named directories reach -prune. Give the repaired command.

    答案

    find jasper \( -name 'build' -o -name 'vendor' \) -prune -o -type f -print

    Only jasper/c prints. Grouping makes either name lead to the pruning action.

  37. 卡片 37

    问题

    GNU find; run from this complete tree's parent. Trailing / marks directories; other entries are regular files. Ignore output order.

    kelp/
kelp/cache/
kelp/cache/a.txt
kelp/b.txt

    find kelp -type f ! -path 'kelp/cache/*' -print

    Compare with:

    find kelp -path 'kelp/cache' -prune -o -type f -print

    Both commands print kelp/b.txt. Which command still visits kelp/cache/a.txt?

    答案

    The first command. Its negated path test hides the descendant from output but does not prevent visiting it; the second command prunes the directory.

  38. 卡片 38

    问题

    GNU find; run from this complete tree's parent. Trailing / marks directories; other entries are regular files. Ignore output order.

    linen/
linen/cache/
linen/cache/a.md
linen/report.md/
linen/report.md/note.txt
linen/b.md

    find linen -type d -name 'cache' -prune -o -type f -name '*.md' -print

    Does directory linen/report.md or its child print?

    答案

    Neither. The directory fails the regular-file guard, and its child fails the .md name test. Only linen/b.md prints; report.md is still traversed.

  39. 卡片 39

    问题

    GNU find; run from this complete tree's parent. Trailing / marks directories; other entries are regular files. Ignore output order.

    moss/
moss/cache/
moss/cache/a
moss/b

    find ./moss -path 'moss/cache' -prune -o -type f -print

    Replace only the path pattern so the cache directory is actually pruned. Give the replacement.

    答案

    './moss/cache'. Encountered paths retain the starting point's ./; the repaired command prints only ./moss/b.

  40. 卡片 40

    问题

    GNU find; run from this complete tree's parent. Trailing / marks directories; other entries are regular files. Ignore output order.

    north/
north/cache/
north/cache/a.c
north/src/
north/src/b.c
north/src/c.h
north/src/folder.h/
north/src/folder.h/d.txt
north/release notes.h

    find north -type d -name 'cache' -prune -o -type f \( -name '*.c' -o -name '*.h' \) -print

    Which paths print?

    答案

    north/src/b.c, north/src/c.h, and north/release notes.h. Pruning excludes the cache subtree; grouping shares the regular-file guard across both suffixes, so folder.h does not print.

A branching folder tree with a glowing teal route to file icons and an amber barrier before a dimmed branch.

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GNU Find Flashcards: Expressions, Output & Pruning

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