Explaining the find -mtime command

Question

I m trying to remove all the dateed logs except the most recent  Before I execute a script to remove the files  I want to of course test my commands to make sure I m bringing up accurate results   When executing these commands the date is   Sep  1 00 53 44 AST 2014   Directory Listing   Aug 27 23 59 testfile 2014-08-27 log Aug 28 23 59 testfile 2014-08-28 log Aug 29 23 59 testfile 2014-08-29 log Aug 30 23 59 testfile 2014-08-30 log Aug 31 23 59 testfile 2014-08-31 log Sep  1 00 29 testfile log   I thought -mtime  1 was supposed to list all files over a day old  Why isn t the 8-30 log one listed   find   -type f -mtime  1 -name  testfile log    testfile 2014-08-27 log   testfile 2014-08-28 log   testfile 2014-08-29 log   This is the desired effect  but it was just trial and error  What is this 0 saying   find   -type f -mtime  0 -name  testfile log    testfile 2014-08-30 log   testfile 2014-08-27 log   testfile 2014-08-28 log   testfile 2014-08-29 log

User · Answer

To find all files modified in the last 24 hours use the one below  The -1 here means changed 1 day or less ago   find   -mtime -1 -ls

User · Answer

1 means 2 days ago  It s rounded

User · Answer

The POSIX specification for find says   -mtimen The primary shall evaluate as true if the file modification time subtracted from the initialization time  divided by 86400  with any remainder discarded   is n   Interestingly  the description of find does not further specify  initialization time    It is probably  though  the time when find is initialized  run    In the descriptions  wherever n is used as a primary argument  it shall be interpreted as a decimal integer optionally preceded by a plus         or minus-sign    -    sign  as follows   n More than n      n Exactly n  -n Less than n   At the given time  2014-09-01 00 53 44 -4 00  where I m deducing that AST is Atlantic Standard Time  and therefore the time zone offset from UTC is -4 00 in ISO 8601 but  4 00 in ISO 9945  POSIX   but it doesn t matter all that much   1409547224   2014-09-01 00 53 44 -04 00 1409457540   2014-08-30 23 59 00 -04 00  so  1409547224 - 1409457540   89684 89684   86400   1  Even if the  seconds since the epoch  values are wrong  the relative values are correct  for some time zone somewhere in the world  they are correct   The n value calculated for the 2014-08-30 log file therefore is exactly 1  the calculation is done with integer arithmetic   and the  1 rejects it because it is strictly a  gt  1 comparison  and not  gt   1

[linux] Explaining the 'find -mtime' command

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