Bash - Date command and space - linux

Question

I am trying to create a script that uses the date command in bash. I am familiar with the basic syntax of the date command.
Here is the simple script:
#!/bin/bash
set -x
DATE_COMMAND="date "+%y-%m-%d %H:%M:%S""
echo "$($DATE_COMMAND)"
set +x
The thing is that the above code doesn't work.
Here is the output:
+ DATE_COMMAND='date +%y-%m-%d'
+ %H:%M:%S
onlyDate: line 3: fg: no job control
+ echo ''
+ set +x
Ok, so the problem is that the bash splits the command because of the space. I can understand that but I don't know how to avoid that. I have tried to avoid the space with \, to avoid the space and the ". Also the single quotes doesn't seem to work.
Please note that I know that this script can be written this way:
#!/bin/bash
set -x
DATE_COMMAND=$(date "+%y-%m-%d %H:%M:%S")
echo "$DATE_COMMAND"
set +x
I have tried that but I can't use this approach because I want to run the command several times in my script.
Any help will be really appreciated!

Answer 1

The correct approach is to define your own function inside your Bash script.
function my_date {
date "+%y-%m-%d %H:%M:%S"
}
Now you can use my_date as if it were an external program.
For example:
echo "It is now $(my_date)."
Or simply:
my_date
Why isn't your approach working?
The first problem is that your assignment is broken.
DATE_COMMAND="date "+%y-%m-%d %H:%M:%S""
This is parsed as an assignment of the string date +%y-%m-%d to the variable DATE_COMMAND. After the blank, the shell starts interpreting the remaining symbols in ways you did not intend.
This could be partially fixed by changing the quotation.
DATE_COMMAND="date '+%y-%m-%d %H:%M:%S'"
However, this doesn't really solve the problem because if we now use
echo $($DATE_COMMAND)
It will not expand the argument correctly. The date program will see the arguments '+%y-%m-%d and %H:%M:%S' (with quotes) instead of a single string. This could be solved by using eval as in
DATE_COMMAND="date '+%y-%m-%d %H:%M:%S'"
echo $(eval $DATE_COMMAND)
where the variable DATE_COMMAND is first expanded to the string date '+%y-%m-%d %H:%M:%S' that is then evaluated as if it were written like so thus invoking date correctly.
Note that I'm only showing this to explain the issue. eval is not a good solution here. Use a function instead.
PS It is better to avoid all-uppercase identifier strings as those are often in conflict with environment variables or even have a magic meaning to the shell.

Answer 2

Escaping the space works for me.
echo `date +%d.%m.%Y\ %R.%S.%3N`

Answer 3

For long scripts
declare variables section:
dateformat="%Y-%m-%d %H:%M:%S"
anywhere to get date:
datestr=`date +"${dateformat}"`
anywhere to echo date:
echo ${datestr}
For short simple scripts DaniëlGu's answer is the best:
echo `date +%d.%m.%Y\ %R.%S.%3N`

Answer 4

Shortest answer is
#if you want to store in a variable
now=$(date '+%F" "%T');
echo $now
#or direct output
date '+%F" "%T'

Answer 5

I'm using:
DF="+%m/%d/%Y %H:%M:%S";
FILE_DATE=$(date "${DF[#]}" -r "${SCHEMA_LOCAL_PATH}.gz");
Seems Bash treats space in $DF as an array's separator and 'date' receives 2 agruments instead of one so I'm sending an array.
Also works for me (check "+" sign):
DF="%m/%d/%Y %H:%M:%S";
FILE_DATE=$(date +"${DF}" -r "${SCHEMA_LOCAL_PATH}.gz");