Come faccio a formattare una data per visualizzarla all’interno di uno script?

La risposta è semplice si usa il comando date o time.

La sintassi è la seguente:
date +FORMAT

Se vuoi visualizzare la data nel formato giorno-mese-anno:

$ date +"%m-%d-%y"

Se vuoi l’anno in 4 cifre:

$ date +"%m-%d-%Y"

Solo la data:

$ date +"%D"

Solo l’orario:

$ date +"%T"

Il giorno della settimana:

$ date +"%A"

Differenti date:

$ date +%Y-%m-%d -d yesterday
2012-03-02

$ date +%A -d yesterday
Thursday

Una attenzione particolare con il comando echo:

$ echo date
date

$ echo `date`
Fri Dec 7 16:57:15 NZDT 2007

Usarlo all’interno di un comando:

ls -l /var/mysql-backup/`date +%A`

Assegnarlo ad una variabile:

$ NOW=$(date +"%m-%d-%Y")
$ echo $NOW

Semplice Shell Script:

#!/bin/bash
NOW=$(date +"%m-%d-%Y")
FILE="backup.$NOW.tar.gz"
# rest of script

Lista completa delle opzioni:

%%     a literal %
%a     locale's abbreviated weekday name (e.g., Sun)
%A     locale's full weekday name (e.g., Sunday)
%b     locale's abbreviated month name (e.g., Jan)
%B     locale's full month name (e.g., January)
%c     locale's date and time (e.g., Thu Mar  3 23:05:25 2005)
%C     century; like %Y, except omit last two digits (e.g., 21)
%d     day of month (e.g, 01)
%D     date; same as %m/%d/%y
%e     day of month, space padded; same as %_d
%F     full date; same as %Y-%m-%d
%g     last two digits of year of ISO week number (see %G)
%G     year of ISO week number (see %V); normally useful only with %V
%h     same as %b
%H     hour (00..23)
%I     hour (01..12)
%j     day of year (001..366)
%k     hour ( 0..23)
%l     hour ( 1..12)
%m     month (01..12)
%M     minute (00..59)
%n     a newline
%N     nanoseconds (000000000..999999999)
%p     locale's equivalent of either AM or PM; blank if not known
%P     like %p, but lower case
%r     locale's 12-hour clock time (e.g., 11:11:04 PM)
%R     24-hour hour and minute; same as %H:%M
%s     seconds since 1970-01-01 00:00:00 UTC
%S     second (00..60)
%t     a tab
%T     time; same as %H:%M:%S
%u     day of week (1..7); 1 is Monday
%U     week number of year, with Sunday as first day of week (00..53)
%V     ISO week number, with Monday as first day of week (01..53)
%w     day of week (0..6); 0 is Sunday
%W     week number of year, with Monday as first day of week (00..53)
%x     locale's date representation (e.g., 12/31/99)
%X     locale's time representation (e.g., 23:13:48)
%y     last two digits of year (00..99)
%Y     year
%z     +hhmm numeric timezone (e.g., -0400)
%Z     alphabetic time zone abbreviation (e.g., EDT)