How do you subtract dates in Unix?
Table of Contents
How do you subtract dates in Unix?
The easiest way is to convert the date to a unix time_t value (i.e. seconds since the beginning of the epoch, or ‘1-1-1970 00:00:00’), and then substract 30 days * 86400 seconds per day from that number. e.g. the following example uses set -x so that you can see the value of the D variable as it changes.
How do I subtract a day from a date in bash?
Set it to the number of days that you want to subtract. Very slight improvement to the command – date –date=”${dataset_date} -${date_diff} day” +%Y-%m-%d.
How do I get the 7 day back date in Unix?
6 Answers
- pday=7 CURRENT= date +”%F %T” –date “$pday days ago” echo $CURRENT how abt this. – jcrshankar.
- That’s fine.
- Likewise, GNU date is unlikely to be installed on a Unix system (likely only Linux and constructs such as Cygwin).
How do you subtract dates in Shell?
In a shell environment/script you can get it with date ‘+%s’ At the time of writing, the current time is 1321358027 . To compare with 2011-11-04 (my birthday), date ‘+%s’ -d 2011-11-04 , yielding 1320361200 . Subtract: expr 1321358027 – 1320361200 gives 996827 seconds, which is expr 996827 / 86400 = 11 days ago.
How do you subtract two timestamps in unix?
In general though, you’ll calculate differences between dates by counting the seconds between them. So your method should be to figure out the unix epoch second for each of your dates, subtract to find the difference, and then print the results in whatever format suits you.
How do you subtract using the shell?
The following arithmetic operators are supported by Bourne Shell….Unix / Linux – Shell Arithmetic Operators Example.
| Operator | Description | Example |
|---|---|---|
| – (Subtraction) | Subtracts right hand operand from left hand operand | `expr $a – $b` will give -10 |
How can I get yesterday’s date in Unix?
- TZ is time zone, EST+24 gives yesterday’s date for Eastern Standard time (like wise you can use EST-24 for tomorrow’s date) +%Y%m%d is the format for YYYYMMDD. – jujuBee.
- This is by far the most succinct version that works on AIX for anyone who is searching for such an answer.
How do you subtract time in bash?
#!/bin/bash DATEONE=”00:02:20″ DATETWO=”00:04:40″ DATE=/bin/date echo $DATEONE echo $DATETWO SECONDSONE=`date -d $DATEONE +%s` SECONDSTWO=`date -d $DATETWO +%s` diff=$(($SECONDSTWO-$SECONDSONE)) echo “$(($diff / 60)) minutes and $(($diff % 60)) seconds elapsed.””
How do I find the difference between two dates in Unix?
- Provide valid time string in A and B.
- Use date -d to handle time strings.
- Use date %s to convert time strings to seconds since 1970 (unix epoche)
- Use bash parameter expansion to subtract seconds.
- divide by seconds per day (86400=60*60*24) to get difference as days.
- ! DST is not taken into account ! See this answer at unix.
What is BC in shell script?
bc (Basic Calculator) is a command line utility that offers everything you expect from a simple scientific or financial calculator. It is a language that supports arbitrary precision numbers with interactive execution of statements and it has syntax similar to that of C programming language.
How do you do mathematical operations in Linux?
We are using the Ubuntu command line, the Terminal, in order to perform all the mathematical operations. You can open the Terminal either through the system Dash or the Ctrl+Alt+T shortcut….Arithmetic.
| +, – | Addition, subtraction |
|---|---|
| *, / , % | Multiplication, division, remainder |
| ** | Exponent value |
How do I get previous day in bash?
Bash get yesterday date
- Yesterday’s date with day of the week and YYYY-MM-DD format: $ date -d “yesterday” ‘+%A, %Y-%m-%d’ Sunday, 2022-04-03.
- Alternatively you can use 1 day ago in your syntax instead of yesterday .
- Day of the week with year, month, day, hour, minutes, and seconds.
How do I get the current date in Linux?
Linux date Command Format Options %D – Display date as mm/dd/yy. %Y – Year (e.g., 2020)
