Chapter 2: Date Manipulation__Linux 101 Hacks
Chapter 2: Date Manipulation
__Linux 101 Hacks
Hack 7. Set System Date and Time
To change the system date use:
#
date {mmddhhmiyyyy.ss}
o mm – Month
o dd – Date
o hh –
24
hour format
o mi – Minutes
o yyyy – Year
o ss – seconds
For example, to set system date to Jan 31st 2009, 10:19 p.m, 53 seconds
#
date 013122192009.53
You can also change system date using set argument as shown below.
#
date 013122192009.53
#
date +%Y%m%d -s "20090131"
#
date -s "01/31/2009 22:19:53"
#
date -s "31 JAN 2009 22:19:53"
#
date set="31 JAN 2009 22:19:53"
To set the time only:
#
date +%T -s "22:19:53"
#
date +%T%p -s "10:19:53PM"
Hack 8. Set Hardware Date and Time
Before setting the hardware date and time, make sure the OS date and timeis set appropriately as shown in the hack#7.
Set the hardware date and time based on the system date as shown below:
#
hwclock –systohc
#
hwclock --systohc –utc
Use hwclock without any parameter, to view the current hardware date andtime:
# maybe sudo hwclock
Check the clock file to verify whether the system is set for UTC:
#
cat /etc/sysconfig/clock
ZONE
=
"
America/Los_Angeles
"
UTC
=
false
ARC
=
false
Hack 9. Display Current Date and Time in a SpecificFormat
Following are different ways of displaying the current date and time invarious formats:
代码
$ date
Thu Jan
1
0
8
:
19
:
23
PST
2009
$ date
--
date
=
"
now
"
Thu Jan
1
0
8
:
20
:
05
PST
2009
$ date
--
date
=
"
today
"
Thu Jan
1
0
8
:
20
:
12
PST
2009
$ date
--
date
=
'
1970-01-01 00:00:01 UTC +5 hours
'
+%
s
18001
$ date
'
+Current Date: %m/%d/%y%nCurrent Time:%H:%M:%S
'
Current Date:
01
/
01
/
0
9
Current Time:0
8
:
21
:
41
$ date
+
"
%d-%m-%Y
"
01
-
01
-
2009
$ date
+
"
%d/%m/%Y
"
01
/
01
/
2009
$ date
+
"
%A,%B %d %Y
"
Thursday,January
01
2009
Following are the different format options you can pass to the datecommand:
代码
o
%
D date (mm
/
dd
/
yy)
o
%
d day of month (
01
..
31
)
o
%
m month (
01
..
12
)
o
%
y last two digits of year (
00
..
99
)
o
%
a locale’s abbreviated weekday name (Sun..Sat)
o
%
A locale’s full weekday name, variable length
(Sunday..Saturday)
o
%
b locale’s abbreviated month name (Jan..Dec)
o
%
B locale’s full month name, variable length
(January..December)
o
%
H hour (
00
..
23
)
o
%
I hour (
01
..
12
)
o
%
Y year (
1970
...)
Hack 10. Display Past Date and Time
Following are various ways to display a past date and time:
代码
$ date
--
date
=
'
3 seconds ago
'
Thu Jan
1
0
8
:
27
:
00
PST
2009
$ date
--
date
=
"
1 day ago
"
Wed Dec
31
0
8
:
27
:
13
PST
2008
$ date
--
date
=
"
1 days ago
"
Wed Dec
31
0
8
:
27
:
18
PST
2008
$ date
--
date
=
"
1 month ago
"
Mon Dec
1
0
8
:
27
:
23
PST
2008
$ date
--
date
=
"
1 year ago
"
Tue Jan
1
0
8
:
27
:
28
PST
2008
$ date
--
date
=
"
yesterday
"
Wed Dec
31
0
8
:
27
:
34
PST
2008
$ date
--
date
=
"
10 months 2 day ago
"
Thu Feb
28
0
8
:
27
:
41
PST
2008
Hack 11. Display Future Date and Time
Following examples shows how to display a future date and time.
代码
$ date
Thu Jan
1
0
8
:
30
:
07
PST
2009
$ date
--
date
=
'
3 seconds
'
Thu Jan
1
0
8
:
30
:
12
PST
2009
$ date
--
date
=
'
4 hours
'
Thu Jan
1
12
:
30
:
17
PST
2009
$ date
--
date
=
'
tomorrow
'
Fri Jan
2
0
8
:
30
:
25
PST
2009
$ date
--
date
=
"
1 day
"
Fri Jan
2
0
8
:
30
:
31
PST
2009
$ date
--
date
=
"
1 days
"
Fri Jan
2
0
8
:
30
:
38
PST
2009
$ date
--
date
=
"
2 days
"
Sat Jan
3
0
8
:
30
:
43
PST
2009
$ date
--
date
=
'
1 month
'
Sun Feb
1
0
8
:
30
:
48
PST
2009
$ date
--
date
=
'
1 week
'
Thu Jan
8
0
8
:
30
:
53
PST
2009
$ date
--
date
=
"
2 months
"
Sun Mar
1
0
8
:
30
:
58
PST
2009
$ date
--
date
=
"
2 years
"
Sat Jan
1
0
8
:
31
:
03
PST
2011
$ date
--
date
=
"
next day
"
Fri Jan
2
0
8
:
31
:
10
PST
2009
$ date
--
date
=
"
-1 days ago
"
Fri Jan
2
0
8
:
31
:
15
PST
2009
$ date
--
date
=
"
this Wednesday
"
Wed Jan
7
00
:
00
:
00
PST
2009