GNU Find Time Flashcards: -mtime, -mmin & Boundaries

Question 1

GNU find: which stored timestamp does -mtime test?

Accepted Answer

The last content-modification time (mtime). It does not mean file creation time.

Question 2

GNU find, no -daystart; starts 2026-10-23 18:00 UTC. Regular files have these mtime ages: fir 7h20m, elm 23h40m, oak 24h20m. Which match -mtime 0?

Accepted Answer

fir and elm. Their ages are inside the first 24-hour range; oak has crossed it. Compare membership, not output order.

Question 3

GNU find, no -daystart; starts 2026-10-23 18:00 UTC. Regular files have these mtime ages: red 12m30s, blue 44m30s, green 45m30s. Which match -mmin -45?

Accepted Answer

red and blue. -mmin -45 selects timestamps newer than the 45-minute cutoff in this fixture.

Question 4

GNU find: what does the c in -ctime refer to?

Accepted Answer

Status-change time. Changes to file data or attributes can update ctime; the c does not stand for creation.

Question 5

GNU find, no -daystart; starts 2026-10-23 18:00 UTC. Regular files have these mtime ages: ash 20h, pine 28h, yew 46h, birch 53h. Which match -mtime 1?

Accepted Answer

pine and yew. The unsigned day test selects the one-day range, between 24 and 48 hours here; it does not select every file older than 24 hours.

Question 6

GNU find; regular file note has stored atime 2026-10-23 17:40 UTC and mtime 2026-10-20 17:40 UTC. At 2026-10-23 18:00 UTC, which tests its recent access: -amin -60 or -mmin -60?

Accepted Answer

-amin -60. It tests the supplied access timestamp. -mmin uses the much older modification timestamp. These are stored timestamps, not a claim that every read updates atime.

Question 7

GNU find, no -daystart; regular files all have past mtimes. Change only the time test in find ./lab -type f -mtime -90 -print to select modifications within the last 90 minutes.

Accepted Answer

Use -mmin -90.

find ./lab -type f -mmin -90 -print

-mtime measures days; -mmin measures minutes. This is an elapsed window, not a calendar day.

Question 8

GNU find, no -daystart; starts 2026-10-23 18:00 UTC. Regular files have these mtime ages: tin 22h, copper 26h, zinc 51h. Which match -mtime +0?

Accepted Answer

copper and zinc. With these off-boundary ages, +0 selects beyond the first 24-hour range. tin is too recent.

Question 9

GNU find; regular files have fixed mtimes in UTC. note is stamped 2026-10-22 09:00:00. Does it match -newermt '2026-10-22 09:00:00 UTC'?

Accepted Answer

No. Newer-than is strict: an identical timestamp fails -newermt.

Question 10

GNU find: complete find ./lab ___ -mtime -1 -print to limit results to regular files.

Accepted Answer

-type f.

find ./lab -type f -mtime -1 -print

The type test excludes directories; -print lists matching paths.

Question 11

GNU find, no -daystart; starts 2026-10-23 18:00 UTC. Regular files have these mtime ages: dawn 44m30s, noon 45m30s. Which match unsigned -mmin 45 in GNU findutils 4.11.0?

Accepted Answer

dawn only. In 4.11.0, unsigned -mmin 45 selects timestamps within the minute immediately newer than the 45-minute cutoff. Do not copy the unsigned -mtime day-range numbering into minute tests.

Question 12

GNU find, no -daystart; starts 2026-10-23 18:00 UTC. Regular files have these mtime ages: clay 46h, slate 49h, chalk 73h. Which match -mtime +1?

Accepted Answer

slate and chalk. +1 goes beyond the one-day range, so 46 hours is too recent. These ages stay away from the exact 48-hour cutoff.

Question 13

GNU find, no -daystart; starts 2026-10-23 18:00 UTC. Regular files have these mtime ages: a 17h, b 47h, c 50h. Which match -mtime -2?

Accepted Answer

a and b. Both are under two 24-hour periods in this fixture; c is beyond that range.

Question 14

GNU find: choose -mtime or -ctime to filter by when file contents were last modified.

Accepted Answer

-mtime. -ctime tracks status changes too, so it is not a substitute when the task specifically asks for content-modification time.

Question 15

GNU find; regular files have fixed mtimes in UTC. a is 2026-10-22 07:00, b 09:00, c 11:00, d 13:00. Which match -newermt '2026-10-22 08:00:00 UTC' ! -newermt '2026-10-22 12:00:00 UTC'?

Accepted Answer

b and c. Both are after 08:00 and no later than 12:00 on October 22. The two adjacent conditions must both succeed.

Question 16

GNU find, no -daystart; starts 2026-10-23 18:00 UTC. Regular files have these mtime ages: iris 44m30s, rose 45m30s. Which match -mmin +45?

Accepted Answer

rose only. +45 tests for a timestamp older than the 45-minute cutoff here. It does not wait for a 46-minute age.

Question 17

GNU find, no -daystart; regular files have past mtimes, none within a minute of a 24-hour boundary. Change only 2 in -mtime 2 to select every file younger than two days.

Accepted Answer

Use -mtime -2. The minus sign selects the younger range; unsigned 2 selects the two-day range instead.

Question 18

GNU find; regular files have fixed mtimes in UTC. a is 2026-10-22 22:00, b 2026-10-23 02:00, c 2026-10-21 22:00. At 2026-10-23 18:00 UTC, which match TZ=UTC find ./lab -daystart -type f -mtime 1 -print?

Accepted Answer

a only. Placing -daystart before -mtime makes this a UTC midnight-based day test. The supplied times avoid midnight endpoints.

Question 19

GNU find: which test takes the literal instant '2026-10-22 12:00:00 UTC': -newer or -newermt?

Accepted Answer

-newermt. Its t means the reference argument is a parsed time. -newer expects a reference file path.

Question 20

GNU find, no -daystart; starts 2026-10-23 18:00 UTC. Regular files have these mtime ages: mint 47h, sage 58h, thyme 71h, basil 74h. Which match -mtime 2?

Accepted Answer

sage and thyme. Their ages fall inside the two-day range, between 48 and 72 hours here. mint is too young; basil is too old.

Question 21

GNU find; regular files have fixed mtimes in UTC. log is stamped 2026-10-22 15:00:00. Does it match ! -newermt '2026-10-22 15:00:00 UTC'?

Accepted Answer

Yes. Equality fails the newer-than test, and ! reverses that result. The negated test includes the bound.

Question 22

GNU find, no -daystart; regular files are aged 23h, 25h and 49h at 2026-10-23 18:00 UTC. Change only +1 in -mtime +1 to select the 25h and 49h files.

Accepted Answer

Use -mtime +0. +1 omits the 25-hour file; +0 includes both stated older files. All three ages are well away from the cutoff.

Question 23

GNU find, no -daystart; starts 2026-10-23 18:00 UTC. Regular files have these mtime ages: a 14m30s, b 16m30s, c 39m30s, d 40m30s. Which match -mmin +15 -mmin -40?

Accepted Answer

b and c. They are older than 15 minutes and younger than 40 minutes. Adjacent tests are combined with AND.

Question 24

GNU find; regular files have fixed mtimes in UTC. a is 2026-10-22 22:00, b 2026-10-22 10:00. At 2026-10-23 18:00 UTC, which match TZ=UTC find ./lab -type f -mtime 1 -daystart -print?

Accepted Answer

b only. -daystart comes too late to affect the earlier -mtime test. The ages are 20 hours and 32 hours; only b is in the elapsed one-day range.

Question 25

GNU find, no -daystart; starts 2026-10-23 18:00 UTC. Regular files have these mtime ages: a 12h, b 30h, c 60h, d 80h. Which match -mtime +0 -mtime -3?

Accepted Answer

b and c. Both pass the older-than-first-range condition and the younger-than-three-days condition. The result is their intersection.

Question 26

GNU find: can -ctime 0 establish that a file was created within the last day?

Accepted Answer

No. It tests recent status change, which can happen to an old file. Creation or birth time is a separate timestamp and is outside this deck's filters.

Question 27

GNU find; regular files have fixed mtimes in UTC. edge is stamped 2026-10-22 06:00:00. Is it selected by -newermt '2026-10-22 06:00:00 UTC' ! -newermt '2026-10-22 10:00:00 UTC'?

Accepted Answer

No. edge equals the lower bound and fails the first, strict newer-than test. The interval excludes its lower endpoint.

Question 28

GNU find, no -daystart; starts 2026-10-23 18:00 UTC. Regular files have these mtime ages: note 90m. Does it match -mtime 1?

Accepted Answer

No. Ninety minutes is still in the first 24-hour range. The number 1 in -mtime 1 does not mean one hour.

Question 29

GNU find, no -daystart; regular files have past mtimes, none near a 24-hour boundary. Change only +3 in -mtime +3 to select files younger than three days.

Accepted Answer

Use -mtime -3. The minus sign selects the younger range. +3 instead selects beyond the three-day range.

Question 30

GNU find: does prefixing a command with TZ=UTC freeze its current time at a particular UTC instant?

Accepted Answer

No. TZ=UTC chooses the timezone for calendar interpretation. The clock still advances, so an elapsed-age exercise must state its initialization time separately.

Question 31

GNU find; regular files have fixed mtimes in UTC. edge is stamped 2026-10-22 10:00:00. Is it selected by -newermt '2026-10-22 06:00:00 UTC' ! -newermt '2026-10-22 10:00:00 UTC'?

Accepted Answer

Yes. edge is after the lower bound and equal to the upper bound. Negating the upper newer-than test includes that equality.

Question 32

GNU find; regular reference file ./ref has mtime 2026-10-22 12:00:00 UTC and lies outside ./lab. Regular files in ./lab have mtimes a 11:59:00, b 12:00:00, c 12:01:00 that day. Which match -newer ./ref?

Accepted Answer

c only. -newer compares each candidate's mtime with the reference file's mtime. Equality fails.

Question 33

GNU find, no -daystart; starts 2026-10-23 18:00 UTC. Regular files have these mtime ages: old 5d20m, recent 4d20m. Which match -mtime +4?

Accepted Answer

old only. +4 goes beyond the four-day range, so the transition is near five days, not four. Both examples avoid the exact cutoff.

Question 34

GNU find, no -daystart; starts 2026-10-23 18:00 UTC. Regular files have these mtime ages: report 90m. Which selects it: -mmin -60 or -mtime -1?

Accepted Answer

-mtime -1 only. Ninety minutes exceeds the 60-minute window but is well within the first 24-hour range.

Question 35

GNU find; regular files have fixed mtimes in UTC. a is 2026-10-22 23:00, b 2026-10-23 03:00, c 2026-10-23 17:00. At 2026-10-23 18:00 UTC, which match TZ=UTC find ./lab -daystart -type f -mtime 0 -print?

Accepted Answer

b and c. With -daystart before the test, these past timestamps fall in the current UTC day range. a is in the previous day. No fixture file is stamped at midnight.

Question 36

GNU find; regular files have fixed mtimes in UTC. a is 2026-10-22 05:59:59, b 06:00:00, c 08:00:00, d 10:00:00, e 10:00:01. Which match -newermt '2026-10-22 06:00:00 UTC' ! -newermt '2026-10-22 10:00:00 UTC'?

Accepted Answer

c and d. The window is (06:00, 10:00] on October 22: after the lower instant, through the upper instant inclusive.

Question 37

GNU find; regular files have fixed mtimes. Change only the test name in find ./lab -type f -newer '2026-10-22 12:00:00 UTC' -print to compare against that literal instant.

Accepted Answer

Use -newermt.

find ./lab -type f -newermt '2026-10-22 12:00:00 UTC' -print

-newer would interpret the argument as a file path.

Question 38

GNU find, no -daystart; regular files have past mtimes, each at least a minute from a 24-hour boundary. Do -mtime 0 and -mtime -1 select the same set?

Accepted Answer

Yes, under these assumptions. Both select the supplied files inside the first 24-hour range. This is not a rule for future timestamps or exact cutoff instants.

Question 39

GNU find, TZ=UTC; regular file journal has mtime 2026-10-22 23:00 UTC. At 2026-10-23 18:00 UTC, does plain -mtime 1 select this file from yesterday?

Accepted Answer

No. It is only 19 hours old. Yesterday's calendar date and the elapsed one-day range are different targets. -daystart before the test changes the reference.

Question 40

GNU find uses -newermt '2026-10-22 06:00:00 UTC' ! -newermt '2026-10-22 10:00:00 UTC' on regular files. Repair the claim “includes 06:00, excludes 10:00” for those UTC instants.

Accepted Answer

Excludes 06:00; includes 10:00. The actual window is (lower, upper], not [lower, upper). Naming calendar boundaries does not reverse the comparisons.

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GNU Find Time Flashcards: -mtime, -mmin & Boundaries