Create timestamp variable in bash script

Question

I am trying to create a timestamp variable in a shell script to make the logging a little easier  I want to create the variable at the beginning of the script and have it print out the current time whenever I issue echo  timestamp  It proving to be more difficult then I thought  Here are some things I ve tried   timestamp   date    T    echo prints out  date    T    timestamp    date    T    echo prints the time when the variable was initialized   Other things I ve tried are just slight variations that didn t work any better  Does anyone know how to accomplish what I m trying to do

User · Accepted Answer

In order to get the current timestamp and not the time of when a fixed variable is defined, the trick is to use a function and not a variable:

#!/bin/bash

# Define a timestamp function
timestamp() {
  date +"%T" # current time
}

# do something...
timestamp # print timestamp
# do something else...
timestamp # print another timestamp
# continue...

If you don't like the format given by the %T specifier you can combine the other time conversion specifiers accepted by date. For GNU date, you can find the complete list of these specifiers in the official documentation here: https://www.gnu.org/software/coreutils/manual/html_node/Time-conversion-specifiers.html#Time-conversion-specifiers

User · Answer

Recent versions of bash don t require call to the external program date   printf -v timestamp     T T          T uses the corresponding argument as a UNIX timestamp  and formats it according to the strftime-style format between the parentheses  An argument of -1 corresponds to the current time  and when no ambiguity would occur can be omitted

User · Answer

timestamp   awk  BEGIN  srand    print srand        srand without a value uses the current timestamp with most Awk implementations

User · Answer

Lots of answer but couldn t find what I was looking for   date   quot  s  3N quot   returns something like   1606297368 210

User · Answer

DATE  date    Y m d    DATE WITH TIME  date    Y m d- H M S    add  3N as we want millisecond too

User · Answer

ISO 8601 format  2018-12-23T12 34 56  is more readable than UNIX timestamp  However on some OSs you cannot have   in the filenames  Therefore I recommend using something like this instead   2018-12-23 12-34-56   You can use the following command to get the timestamp in this format   TIMESTAMP  date   Y- m- d  H- M- S    This is the format I have seen many applications use  Another nice thing about this is that if your file names start with this  you can sort them alphabetically and they would be sorted by date

User · Answer

You can use  timestamp  date --rfc-3339 seconds    This delivers in the format 2014-02-01 15 12 35-05 00  The back-tick     characters will cause what is between them to be evaluated and have the result included in the line   date --help has other options

User · Answer

If you want to get unix timestamp  then you need to use   timestamp   date   s     T will give you just the time  same as  H  M  S  via http   www cyberciti biz faq linux-unix-formatting-dates-for-display

User · Answer

Use command substitution   timestamp    date   T

User · Answer

I am using ubuntu 14 04   The correct way in my system should be date   s   The output of date   T is like 12 25 25

User · Answer

And for my fellow Europeans  try using this   timestamp   date   d- m- Y  H- M- S    will give a format of the format   15-02-2020 19-21-58   You call the variable and get the string representation like this    timestamp

[bash] Create timestamp variable in bash script

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