GNU Find Permission Flashcards: Exact, All & Any Bits

Question 1

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

Accepted Answer

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

Question 2

In GNU find, what does -perm 0640 require?

Accepted Answer

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

Question 3

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

Accepted Answer

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

Question 4

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

Accepted Answer

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

Question 5

Which files lack owner execute permission?

Regular files; special bits are 0:

memo  0640
runner  0750
shared  0660

Accepted Answer

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

Question 6

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

Regular files; special bits are 0:

note  0620
copy  0660
tool  0720
open  0622

Accepted Answer

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

Question 7

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

Regular files; special bits are 0:

amber  0410
birch  0650
cedar  0600
dune  0040

Accepted Answer

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

Question 8

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

Regular files; special bits are 0:

iris  0600
jade  0620
kelp  0602
lime  0622

Accepted Answer

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

Question 9

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

Accepted Answer

-perm -0201

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

Question 10

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

Accepted Answer

-perm 0610

There is no prefix: every mode bit must agree.

Question 11

Rewrite GNU -perm -0050 using a symbolic mode.

Accepted Answer

-perm -g=rx

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

Question 12

Rewrite GNU -perm /0102 using a symbolic mode.

Accepted Answer

-perm /u=x,o=w

Owner execute OR other write is enough.

Question 13

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

Regular files; special bits are 0:

draft  0660
public  0644
private  0600
script  0750

Accepted Answer

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

Question 14

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

Accepted Answer

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

Question 15

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

Accepted Answer

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

Question 16

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

Accepted Answer

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.

Question 17

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

Accepted Answer

-perm -0020 ! -perm -0004

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

Question 18

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

Accepted Answer

-0041, giving -perm -0041.

Both selected bits must be present.

Question 19

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

Accepted Answer

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

Question 20

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

Accepted Answer

-perm /0120

Either selected bit is sufficient.

Question 21

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

Accepted Answer

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

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

Question 22

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

Regular files; special bits are 0:

a  0040
b  0640
c  0440

Accepted Answer

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

Question 23

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

Regular files; special bits are 0:

a  0650
b  0640
c  0610
d  0600

Accepted Answer

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

Question 24

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

Accepted Answer

/ (any selected bit).

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

Question 25

Does this GNU command restrict BOTH branches to regular files?

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

Accepted Answer

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.

Question 26

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

Regular files; special bits are 0:

a  0000
b  0400
c  0600

Accepted Answer

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

Question 27

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

Accepted Answer

! -perm /0022

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

GNU Find Permission Flashcards: Exact, All & Any Bits

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GNU Find Permission Flashcards: Exact, All & Any Bits

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