CODEWITHSUNDEEP
linuxbashcommand-line
flybywire
flybywire

Reputation: 273532

how do I check in bash whether a file was created more than x time ago?

I want to check in linux bash whether a file was created more than x time ago.

let's say the file is called text.txt and the time is 2 hours.

 if [ what? ]
 then
     echo "old enough"
 fi

Upvotes: 122

Views: 134736

Answers (9)

Pamputt
Pamputt

Reputation: 440

Since coreutils 8.31, glibc 2.28 and kernel version 4.11 or newer, stat returns the creation date of a file. To retrieve the creation date

file_creation_date=`stat -c '%w' text.txt`

We retrieve the time it was two hours ago

two_hours_ago=`date -u +"%F %T" -d '2 hours ago'`

And, we compare the two dates

if [[ $file_creation_date > $two_hours_ago ]]; then
    echo "older"
fi

Upvotes: 0

Guss
Guss

Reputation: 32335

Using the stat to figure out the last modification date of the file, date to figure out the current time and a liberal use of bashisms, one can do the test that you want based on the file's last modification time1.

if [ "$(( $(date +"%s") - $(stat -c "%Y" "$somefile") ))" -gt "7200" ]; then
   echo "'$somefile' is older then 2 hours"
fi

While the code is a bit less readable then the find approach, I think its a better approach then running find to look at a file you already "found". Also, date manipulation is fun ;-)

  1. As Phil correctly noted creation time is not recorded, but use %Z instead of %Y below to get "change time" which may be what you want.

[Update]

For mac users, use stat -f "%m" "$somefile" instead of the Linux specific syntax above

Upvotes: 34

kmkaplan
kmkaplan

Reputation: 18960

Only for modification time

if test `find "text.txt" -mmin +120`
then
    echo old enough
fi

You can use -cmin for change or -amin for access time. As others pointed I don’t think you can track creation time.

Upvotes: 167

xpmatteo
xpmatteo

Reputation: 11408

I use

file_age() {
    local filename=$1
    echo $(( $(date +%s) - $(date -r $filename +%s) ))
}

is_stale() {
    local filename=$1
    local max_minutes=20
    [ $(file_age $filename) -gt $(( $max_minutes*60 )) ]
}

if is_stale /my/file; then
    ...
fi

Upvotes: 0

nemik
nemik

Reputation: 668

I always liked using date -r /the/file +%s to find its age.

You can also do touch --date '2015-10-10 9:55' /tmp/file to get extremely fine-grained time on an arbitrary date/time.

Upvotes: 52

Vide
Vide

Reputation: 91

The find one is good but I think you can use anotherway, especially if you need to now how many seconds is the file old

date -d "now - $( stat -c "%Y" $filename ) seconds" +%s

using GNU date

Upvotes: 9

Maryam Jeddian
Maryam Jeddian

Reputation: 261

Although ctime isn't technically the time of creation, it quite often is.

Since ctime it isn't affected by changes to the contents of the file, it's usually only updated when the file is created. And yes - I can hear you all screaming - it's also updated if you change the access permissions or ownership... but generally that's something that's done once, usually at the same time you put the file there.

Personally I always use mtime for everything, and I imagine that is what you want. But anyway... here's a rehash of Guss's "unattractive" bash, in an easy to use function.

#!/bin/bash
function age() {
   local filename=$1
   local changed=`stat -c %Y "$filename"`
   local now=`date +%s`
   local elapsed

   let elapsed=now-changed
   echo $elapsed
}

file="/"
echo The age of $file is $(age "$file") seconds.

Upvotes: 13

fdr
fdr

Reputation: 391

Consider the outcome of the tool 'stat':

  File: `infolog.txt'
  Size: 694         Blocks: 8          IO Block: 4096   regular file
Device: 801h/2049d  Inode: 11635578    Links: 1
Access: (0644/-rw-r--r--)  Uid: ( 1000/     fdr)   Gid: ( 1000/     fdr)
Access: 2009-01-01 22:04:15.000000000 -0800
Modify: 2009-01-01 22:05:05.000000000 -0800
Change: 2009-01-01 22:05:05.000000000 -0800

You can see here the three dates for Access/modify/change. There is no created date. You can only really be sure when the file contents were modified (the "modify" field) or its inode changed (the "change" field).

Examples of when both fields get updated:

"Modify" will be updated if someone concatenated extra information to the end of the file.

"Change" will be updated if someone changed permissions via chmod.

Upvotes: 5

Philip Reynolds
Philip Reynolds

Reputation: 9392

Creation time isn't stored.

What are stored are three timestamps (generally, they can be turned off on certain filesystems or by certain filesystem options):

  • Last access time
  • Last modification time
  • Last change time

a "Change" to the file is counted as permission changes, rename etc. While the modification is contents only.

Upvotes: 17

Related Questions