How to convert file dates to a particular format when using 'ls'

Question

I have the following input data:

-rw-rw-r--. 1 abmnyu abmnyu 0 Dec 30 07:06 ffd_in_imp_bus.dat
-rw-rw-r--. 1 abmnyu abmnyu 0 Dec 30 07:06 ffd_ik_imp_bus.dat

I need Dec 30 to be displayed in the format 20171230 while using ls -l, as shown below:

-rw-rw-r--. 1 abmnyu abmnyu 0 20171230 07:06 ffd_in_imp_bus.dat
-rw-rw-r--. 1 abmnyu abmnyu 0 20171230 07:06 ffd_ik_imp_bus.dat

Answer 1

If you're using GNU ls (this is standard on Linux systems), it has a --time-style option which can be used to change the date/time format.

The built-in format closest to what you want is long-iso.

e.g.

$ ls -l --time-style=long-iso
total 1
-rw-r--r-- 1 cas cas 0 2017-12-30 21:26 ffd_ik_imp_bus.dat
-rw-r--r-- 1 cas cas 0 2017-12-30 21:26 ffd_in_imp_bus.dat

You can also use a custom format using the same date formatting specification as in GNU date:

$ ls -l --time-style='+%Y%m%d %H:%M'
total 1
-rw-r--r-- 1 cas cas 0 20171230 21:26 ffd_ik_imp_bus.dat
-rw-r--r-- 1 cas cas 0 20171230 21:26 ffd_in_imp_bus.dat

From man ls:

--time-style=STYLE

with -l, show times using style STYLE: full-iso, long-iso, iso, locale, or +FORMAT

FORMAT is interpreted like in `date'

if FORMAT is FORMAT1<newline>FORMAT2, then FORMAT1 applies to non-recent files and FORMAT2 to recent files.

if STYLE is prefixed with posix-, STYLE takes effect only outside the POSIX locale