Shell Bash get datetime and format

https://stackoverflow.com/questions/1401482/yyyy-mm-dd-format-date-in-shell-script

In bash (>=4.2) it is preferable to use printf's built-in date formatter (part of bash) rather than the external date (usually GNU date).

As such:

# put current date as yyyy-mm-dd in $date

# -1 -> explicit current date, bash >=4.3 defaults to current time if not provided

# -2 -> start time for shell

printf -v date '%(%Y-%m-%d)T\n' -1 

# put current date as yyyy-mm-dd HH:MM:SS in $date

printf -v date '%(%Y-%m-%d %H:%M:%S)T\n' -1 

# to print directly remove -v flag, as such:

printf '%(%Y-%m-%d)T\n' -1

# -> current date printed to terminal

In bash (<4.2):

# put current date as yyyy-mm-dd in $date

date=$(date '+%Y-%m-%d')

# put current date as yyyy-mm-dd HH:MM:SS in $date

date=$(date '+%Y-%m-%d %H:%M:%S')

# print current date directly

echo $(date '+%Y-%m-%d')

Other available date formats can be viewed from the date man pages (for external non-bash specific command):

https://stackoverflow.com/questions/10067266/when-to-wrap-quotes-around-a-shell-variable#:~:text=General%20rule%3A%20quote%20it%20if,a%20single%20argument%20into%20many.

https://stackoverflow.com/questions/13659318/how-to-remove-space-from-string

https://stackoverflow.com/questions/32481877/what-are-nr-and-fnr-and-what-does-nr-fnr-imply

https://stackoverflow.com/questions/56893177/are-there-any-benefits-of-ending-a-bash-script-with-exit