Hi, I've got a shell script which does the following to store the current day's date in a variable 'dt':
date "+%a %d/%m/%Y" | read dt
echo ${dt}
How would i go about getting yesterdays date into a variable?
Basically what i'm trying to achieve is to use grep to pull all of yesterday's lines from a log file, since each line in the log contains the date in "Mon 01/02/2010" format.
Thanks a lot
You have atleast 2 options
Use perl:
perl -e '@T=localtime(time-86400);printf("%02d/%02d/%02d",$T[4]+1,$T[3],$T[5]+1900)'
Install GNU date (it's in the sh_utils package if I remember correctly)
date --date yesterday "+%a %d/%m/%Y" | read dt
echo ${dt}
Not sure if this works, but you might be able to use a negative timezone. If you use a timezone that's 24 hours before your current timezone than you can simply use date.
If you are on a Mac or BSD or something else without the --date option, you can use:
date -r `expr \`date +%s\` - 86400` '+%a %d/%m/%Y'
Update: or perhaps...
date -r $((`date +%s` - 86400)) '+%a %d/%m/%Y'
If you have Perl available (and your date doesn't have nice features like yesterday), you can use:
pax> date
Thu Aug 18 19:29:49 XYZ 2010
pax> dt=$(perl -e 'use POSIX;print strftime "%d/%m/%Y%",localtime time-86400;')
pax> echo $dt
17/08/2010
Thanks for the help everyone, but since i'm on HP-UX (after all: the more you pay, the less features you get...) i've had to resort to perl:
perl -e '@T=localtime(time-86400);printf("%02d/%02d/%04d",$T[3],$T[4]+1,$T[5]+1900)' | read dt
If your HP-UX installation has Tcl installed, you might find it's date arithmetic very readable (unfortunately the Tcl shell does not have a nice "-e" option like perl):
dt=$(echo 'puts [clock format [clock scan yesterday] -format "%a %d/%m/%Y"]' | tclsh)
echo "yesterday was $dt"
This will handle all the daylight savings bother.