GNU Find Permission Flashcards: Exact, All & Any Bits

このデッキのカード

1. カード 1

   質問

   A regular file has mode 0541 (special bits 0). Which octal bit would add owner write permission?

   回答

   0200. Owner permissions occupy the hundreds digit; write contributes 2.

2. カード 2

   質問

   In GNU find, what does -perm 0640 require?

   回答

   Exactly mode 0640, including no special bits. Extra read, write, execute, or special bits prevent a match.

3. カード 3

   質問

   In GNU find, what does the minus prefix in -perm -0240 mean?

   回答

   Both selected bits must be set: owner write and group read. Unselected bits may have either value.

4. カード 4

   質問

   In GNU find, what does the slash prefix in -perm /0104 mean?

   回答

   At least one selected bit must be set: owner execute or other read. Both may also be set.

5. カード 5

   質問

   Which files lack owner execute permission?

   Regular files; special bits are 0:

   memo  0640
   runner  0750
   shared  0660
   

   回答

   memo and shared. Their owner digit is 6 (read + write); runner has owner digit 7.

6. カード 6

   質問

   Which file matches GNU find . -type f -perm 0620?

   Regular files; special bits are 0:

   note  0620
   copy  0660
   tool  0720
   open  0622
   

   回答

   note only. Each other mode has at least one extra bit.

7. カード 7

   質問

   Which files match GNU find . -type f -perm -0410?

   Regular files; special bits are 0:

   amber  0410
   birch  0650
   cedar  0600
   dune  0040
   

   回答

   amber and birch. Both have owner read (0400) and group execute (0010).

8. カード 8

   質問

   Which files match GNU find . -type f -perm /0022?

   Regular files; special bits are 0:

   iris  0600
   jade  0620
   kelp  0602
   lime  0622
   

   回答

   jade, kelp, and lime. Group write or other write is enough.

9. カード 9

   質問

   Write one numeric GNU -perm predicate requiring owner write AND other execute, allowing any extra bits.

   回答

   -perm -0201

   The mask combines owner write (0200) and other execute (0001).

10. カード 10

    質問

    Write a numeric GNU -perm predicate for exactly owner read/write, group execute, no other permissions, and no special bits.

    回答

    -perm 0610

    There is no prefix: every mode bit must agree.

11. カード 11

    質問

    Rewrite GNU -perm -0050 using a symbolic mode.

    回答

    -perm -g=rx

    Group read AND group execute are required; other bits are ignored.

12. カード 12

    質問

    Rewrite GNU -perm /0102 using a symbolic mode.

    回答

    -perm /u=x,o=w

    Owner execute OR other write is enough.

13. カード 13

    質問

    Which files match GNU find . -type f ! -perm /0111?

    Regular files; special bits are 0:

    draft  0660
    public  0644
    private  0600
    script  0750
    

    回答

    draft, private, and public. Negating an any-execute test selects files with no execute bits.

14. カード 14

    質問

    Which files match GNU find . -type f -perm /0000 in current GNU find?

    Regular files; special bits are 0:

    sealed  0000
    text  0640
    run  0700
    

    回答

    All three files. GNU find treats an empty any-bit mask as matching everything; this is a special case.

15. カード 15

    質問

    A regular file has mode 0641 (special bits 0). Which single bit makes GNU -perm 0640 fail?

    回答

    Other execute (0001). Exact matching rejects that extra bit.

16. カード 16

    質問

    Does GNU -perm -0200 prove the invoking user can successfully write the file?

    回答

    No. It checks the owner-write mode bit, regardless of who invokes find. ACLs, the filesystem, and other conditions can affect access; even -writable is not a guarantee that a later write succeeds.

17. カード 17

    質問

    Write two GNU -perm predicates joined by implicit AND: require group write, but forbid other read. Extra bits are allowed.

    回答

    -perm -0020 ! -perm -0004

    The first requires group write; the negated second excludes other read.

18. カード 18

    質問

    GNU -perm /0041 also accepts files with just one selected bit. Replace only its mode argument to require group read AND other execute.

    回答

    -0041, giving -perm -0041.

    Both selected bits must be present.

19. カード 19

    質問

    A regular file log and a directory box both have mode 0750 (special bits 0). Which matches GNU find . -type f -perm 0750?

    回答

    log only. -type f restricts the result to regular files; -perm alone does not.

20. カード 20

    質問

    Write one numeric GNU -perm predicate selecting a file with owner execute OR group write, allowing extra bits.

    回答

    -perm /0120

    Either selected bit is sufficient.

21. カード 21

    質問

    Write a complete GNU find command under . selecting only regular files with mode exactly 0604 OR exactly 0640. All mode bits must agree.

    回答

    find . -type f \( -perm 0604 -o -perm 0640 \) -print

    The parentheses keep the regular-file condition outside both alternatives.

22. カード 22

    質問

    Which file matches GNU find . -type f -perm g=r?

    Regular files; special bits are 0:

    a  0040
    b  0640
    c  0440
    

    回答

    a only. In this exact symbolic test, the mask starts from zero, so g=r means exactly 0040.

23. カード 23

    質問

    Which files match GNU find . -type f ! -perm -0050?

    Regular files; special bits are 0:

    a  0650
    b  0640
    c  0610
    d  0600
    

    回答

    b, c, and d. At least one required group bit is missing; the negation does not require both bits to be absent.

24. カード 24

    質問

    Which GNU -perm matching prefix is a GNU extension: no prefix, -, or /?

    回答

    / (any selected bit).

    Exact and minus-prefixed matching are specified by POSIX. Do not use obsolete GNU +mode as an alternative.

25. カード 25

    質問

    Does this GNU command restrict BOTH branches to regular files?

    find . -type f -perm 0604 -o -perm 0640
    

    回答

    No. Implicit AND binds more tightly than -o, so the 0640 branch can also match a directory. Group the two permission alternatives after -type f.

26. カード 26

    質問

    Which files match GNU find . -type f -perm 0000?

    Regular files; special bits are 0:

    a  0000
    b  0400
    c  0600
    

    回答

    a only. With no matching prefix, zero means exactly no ordinary or special mode bits.

27. カード 27

    質問

    Write a GNU -perm expression selecting files with NEITHER group write NOR other write, allowing all other bits.

    回答

    ! -perm /0022

    Negate the any-bit test. ! -perm -0022 would also accept files that have just one of the two write bits.

27枚のカード

GNU Find Permission Flashcards: Exact, All & Any Bits

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