#!/bin/bash
cd /home/pi/cc/uvreadings
while true
do
ATIME=`stat -c %Z /home/pi/cc/uvreadings/uvreadings.log`
if [[ "$ATIME" < "$LTIME" ]]
then
echo "log file not updated for +24 hours"
else
echo "log file WAS updated in last +24 hours"
fi
sleep 10
done
I am trying to check if a file has been modified in the last 24 hours by comparing atime to Ltime
atime will always be less than ltime
so can i modify the statement
if [[ "$ATIME" < "$LTIME" ]]
to
if [[ "$ATIME +1 day" < "$LTIME" ]]`
of is the a better way to achieve this
thanks for any advice
First of all, there are (at least) three different timestamps on a file, and you seem to have them mixed up. You talk about atime, the %Z option instead gives you ctime, and it sounds like what you want is actually mtime: the time at which the file's contents last changed. You can get mtime with stat -c %Y.
To see if it was less than one day ago, you can indeed add one day to it; but the time is in seconds, so you need to add 24*60*60 seconds. The easiest way to do that is probably with arithmetic expansion. It could look something like this:
if [[ $((MTIME + (24 * 60 * 60))) > $LTIME ]] # modified in the last day
I assume you wrote code to get the current time and store it in LTIME, even though you didn't show that code in your question. It has to go inside the loop, of course. One way to do that would be
LTIME=`date +%s`
Related
I have a file in which i have following content
2020-07-30 14:28:02|INFO|0||agent 1|CUpload|CUploadService
2020-07-30 14:28:02|INFO|0||agent 1|CUpload|CUpload
2020-07-30 14:28:04|INFO|0||agent 1|CUpload|CUplo
I need to write a script through which i can calculate the time difference. If time is more than 60 minutes since the file updated last time, i need to write the column 3 in another file.
I am able to get the date in right format but i dont know how to take difference so it will tell me if it has been more than 60 mins or not.
date +%Y-%m-%d" "%H:%M:%S
2020-07-30 14:47:24
I have placed two times in a file and took their difference but it came out to be zero
more 3.unl | awk -F '|' '{print$2 - $1}'
One possibility: convert date and time to epoch and subtract, eg:
#!/bin/bash
first='2020-07-30 14:28:04'
later='2020-07-30 15:39:09'
ep1=$(date --date="$first" +%s)
ep2=$(date --date="$later" +%s)
diff=$((ep2 - ep1))
echo diff $diff
if (( $diff > 3600 )); then
echo actions ...
fi
I have this script I am building and need a bit of help. I want to use as minimal lines of code as possible. However what I want the script to do is the following.
Backup a specified file such as authlog into a new file with the keywords I specify.
However. I also want it to back up the file if current backed up file is older than 2+ days ago and if it is newer. Leave it alone. if (file) is older than +2 days old delete it and replace it with an updated one.
I'm getting integer expression expected and I'm not sure how to fix it
#!/bin/bash
authlog=/home/(myhomedir)/logs/backups/authlog-${current_date}
backup="$(cat /var/log/auth.log | grep -e failed -e invalid > /home/(myhomedir)/logs/backup)"
dayold=$(date -d '1 day ago' "+%Y-%m-%d")
current_date=$(date +"%m_%d_%Y")
if [ $authlog -lt $dayold ] ;
then ${backup}
else
echo $authlog is newer than $current_date $authlog has not been updated
if [ $authlog -eq ${current_date} ]
then "$(rm {authlog})"
fi
fi
You can't use -lt to compare non-numeric strings. This is why you're getting "integer expression expected". You're trying to compare a filename to a date string.
The easiest way to compare dates is by converting them to seconds since epoch (Jan 1, 1970 00:00:00 UTC). As an example, suppose I have a file called foo.bar and I want to check if it was last modified 3 or more days ago:
filetime=$(stat -c %Y foo.bar)
three_days_ago=$(date -d "3 days ago" +%s)
if [ $filetime -lt $three_days_ago ]; then
echo "foo.bar was last modified more than 3 days ago"
fi
Also, your authlog variable does not contain a date. I'm assuming there's a missing step that you forgot.
I have a shell script that runs on Linux and uses this call to get yesterday's date in YYYY-MM-DD format:
date -d "1 day ago" '+%Y-%m-%d'
It works most of the time, but when the script ran yesterday morning at 2013-03-11 0:35 CDT it returned "2013-03-09" instead of "2013-03-10".
Presumably daylight saving time (which started yesterday) is to blame. I'm guessing the way "1 day ago" is implemented it subtracted 24 hours, and 24 hours before 2013-03-11 0:35 CDT was 2013-03-09 23:35 CST, which led to the result of "2013-03-09".
So what's a good DST-safe way to get yesterday's date in bash on Linux?
I think this should work, irrespective of how often and when you run it ...
date -d "yesterday 13:00" '+%Y-%m-%d'
Under Mac OSX date works slightly different:
For yesterday
date -v-1d +%F
For Last week
date -v-1w +%F
This should also work, but perhaps it is too much:
date -d #$(( $(date +"%s") - 86400)) +"%Y-%m-%d"
If you are certain that the script runs in the first hours of the day, you can simply do
date -d "12 hours ago" '+%Y-%m-%d'
BTW, if the script runs daily at 00:35 (via crontab?) you should ask yourself what will happen if a DST change falls in that hour; the script could not run, or run twice in some cases. Modern implementations of cron are quite clever in this regard, though.
Here a solution that will work with Solaris and AIX as well.
Manipulating the Timezone is possible for changing the clock some hours.
Due to the daylight saving time, 24 hours ago can be today or the day before yesterday.
You are sure that yesterday is 20 or 30 hours ago. Which one? Well, the most recent one that is not today.
echo -e "$(TZ=GMT+30 date +%Y-%m-%d)\n$(TZ=GMT+20 date +%Y-%m-%d)" | grep -v $(date +%Y-%m-%d) | tail -1
The -e parameter used in the echo command is needed with bash, but will not work with ksh.
In ksh you can use the same command without the -e flag.
When your script will be used in different environments, you can start the script with #!/bin/ksh or #!/bin/bash. You could also replace the \n by a newline:
echo "$(TZ=GMT+30 date +%Y-%m-%d)
$(TZ=GMT+20 date +%Y-%m-%d)" | grep -v $(date +%Y-%m-%d) | tail -1
date -d "yesterday" '+%Y-%m-%d'
To use this later:
date=$(date -d "yesterday" '+%Y-%m-%d')
you can use
date -d "30 days ago" +"%d/%m/%Y"
to get the date from 30 days ago, similarly you can replace 30 with x amount of days
Just use date and trusty seconds:
As you rightly point out, a lot of the details about the underlying computation are hidden if you rely on English time arithmetic. E.g. -d yesterday, and -d 1 day ago will have different behaviour.
Instead, you can reliably depend on the (precisely documented) seconds since the unix epoch UTC, and bash arithmetic to obtain the moment you want:
date -d #$(( $(date +"%s") - 24*3600)) +"%Y-%m-%d"
This was pointed out in another answer. This form is more portable across platforms with different date command line flags, is language-independent (e.g. "yesterday" vs "hier" in French locale), and frankly (in the long-term) will be easier to remember, because well, you know it already. You might otherwise keep asking yourself: "Was it -d 2 hours ago or -d 2 hour ago again?" or "Is it -d yesterday or -d 1 day ago that I want?"). The only tricky bit here is the #.
Armed with bash and nothing else:
Bash solely on bash, you can also get yesterday's time, via the printf builtin:
%(datefmt)T
causes printf to output the date-time string resulting from using
datefmt as a format string for strftime(3). The corresponding argu‐
ment is an integer representing the number of seconds since the
epoch. Two special argument values may be used: -1 represents the
current time, and -2 represents the time the shell was invoked.
If no argument is specified, conversion behaves as if -1 had
been given.
This is an exception to the usual printf behavior.
So,
# inner printf gets you the current unix time in seconds
# outer printf spits it out according to the format
printf "%(%Y-%m-%d)T\n" $(( $(printf "%(%s)T" -1) - 24*3600 ))
or, equivalently with a temp variable (outer subshell optional, but keeps environment vars clean).
(
now=$(printf "%(%s)T" -1);
printf "%(%Y-%m-%d)T\n" $((now - 24*3600));
)
Note: despite the manpage stating that no argument to the %()T formatter will assume a default -1, i seem to get a 0 instead (thank you, bash manual version 4.3.48)
You can use:
date -d "yesterday 13:55" '+%Y-%m-%d'
Or whatever time you want to retrieve will retrieved by bash.
For month:
date -d "30 days ago" '+%Y-%m-%d'
As this question is tagged bash "DST safe":
And using fork to date command implie delay, there is a simple and more efficient way using pure bash built-in:
printf -v tznow '%(%z %s)T' -1
TZ=${tznow% *} printf -v yesterday '%(%Y-%m-%d)T' $(( ${tznow#* } - 86400 ))
echo $yesterday
This is a lot quicker on more system friendly than having to fork to date.
From bash version 5.0, there is a new variable $EPOCHSECONDS
printf -v tz '%(%z)T' -1
TZ=$tz printf -v yesterday '%(%Y-%m-%d)T' $(( EPOCHSECONDS - 86400 ))
echo $yesterday
I am well aware of being able to do find myfile.txt -mtime +5 to check if my file is older than 5 days or not. However I would like to fetch mtime in days of myfile.txt and store it into a variable for further usage. How would I do that?
stat can give you that info:
filemtime=$(stat -c %Y myfile.txt)
%Y gives you the last modification as "seconds since The Epoch", but there are lots of other options; more info. So if the file was modified on 2011-01-22 at 15:30 GMT, the above would return a number in the region of 1295710237.
Edit: Ah, you want the time in days since it was modified. That's going to be more complicated, not least because a "day" is not a fixed period of time (some "days" have only 23 hours, others 25 — thanks to daylight savings time).
The naive version might look like this:
filemtime=$(stat -c %Y "$1")
currtime=$(date +%s)
diff=$(( (currtime - filemtime) / 86400 ))
echo $diff
...but again, that's assuming a day is always exactly 86,400 second long.
More about arithmetic in bash here.
The date utility has a convenient switch for extracting the mtime from a file, which you can then display or store using a format string.
date -r file "+%F"
# 2021-01-12
file_mtime=$(date -r file "+%F")
See man date, the output of date is controlled by a format string beginning with "+"
Useful format strings for comparing many dates might include:
"+%j": day of year
"+%s": unix epoch time
Arithmetic with dates is a bit of a pain in bash, so if you need relative time that will work in all corner cases, you may be better off with another language.
AGE=$(perl -e 'print -M $ARGV[0]' $file)
will set $AGE to the age of $file in days, as Perl's -M operator handles the stat call and the conversion to days for you.
The return value is a floating-point value (e.g., 6.62849537 days). Add an int to the expression if you need to have an integer result
AGE=$(perl -e 'print int -M $ARGV[0]' $file)
Ruby and Python also have their one-liners to stat a file and return some data, but I believe Perl has the most concise way.
I this the answer?
A=$(stat -c "%y" myfile.txt)
look at stat-help
stat --help
Usage: stat [OPTION]... FILE...
Display file or file system status.
[...]
-c --format=FORMAT use the specified FORMAT instead of the default;
output a newline after each use of FORMAT
[...]
The valid format sequences for files
[...]
%y Time of last modification, human-readable
%Y Time of last modification, seconds since Epoch
[...]
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
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.
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.
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 "'$somefile' is older then 2 hours"
fi
While the code is a bit less readable then the find approach, I think its a better approach then running find to look at a file you already "found". Also, date manipulation is fun ;-)
As Phil correctly noted creation time is not recorded, but use %Z instead of %Y below to get "change time" which may be what you want.
[Update]
For mac users, use stat -f "%m" "$somefile" instead of the Linux specific syntax above
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.
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.
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
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.
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