Shell script to get previous date 6

[babeo]

Hi
I write a script to create file with name of previous date, but get stuck on how to get the previous date:
#!/bin/sh
date +%d > TODAY
TODAY -=TODAY #this is I want to make previous day
touch myserver>mydir/myfile.TODAY1200
--------

you can see line 2, I just want to get the date only to be stored in TODAY file, then I get stuck on the next line.
Is there any command to get the previous date or could someone figures out my terrible script please.

Thanks.

 

[cgswong]

First off, the statement "date +%d > TODAY" pipes the output of the date command to a file named TODAY. Hence the statement(s) following would not work. What you need to do is convert the TODAY variable to an expression (it's then a number) after which you can apply arithmetic operands to it. Try the following, it should work:

TODAY=`date +%d`
TODAY=`expr $TODAY - 1`
echo $TODAY

Hope this helps.

- Stuart

 

[babeo]

Wow, thanks

It works finally, however, it does not work properly !!
here is my result:

myfile.10101

The script is ran today as of Jan 02, 2001, and I expect to have file created as myfile.010101, but the zero of the day is missing, and I need that zero, how can I fix that problem ? (I think if the day is either 1x or 2x or 3x then I don't have any problem of leading zero, but for days from 1-9, I have leading zero and it is the problem.)

Thanks a lot

 

[grega]

Seems good in principle, but what if you run on the 1st of June say?, the expression won't return 31 (for May), but zero. What I do/have done is either ...

1. Use my database server to return a date in whatever format I specify (my preferred method nowadays)

or

2. Maintain a file called yesterday in a specified directory containing the date I need. Then at 11:59pm every night, I write the date to it (using a small script running in cron). So next day, if I need the previous days date, I just "cat" the contents of the file, using something like

FILENAME=myfile.`cat /home/yesterday`

Unfortunately Unix (on it's own) is not of very much use when it comes to date calculations.

Greg.

 

[babeo]

Thanks Greg for your figure out. You're right.

I think I will try your way.
Thank again all

 

[jad]

TODAY=`date "+%y %m %d" | nawk '{split("31,31,28,31,30,31,30,31,31,30,31,30",month,"," if ($1 % 4 == 0) {month[3]=29;}; day=$3-1; if (day == 0) {day=month[$2-0];} printf("%02d",day);}'`
echo $TODAY

yeah i know ... but it works

 

[grega]

It does jad, but it makes my head hurt! :-\ .. lol

Greg.

 

[abovebrd]

How would you subtract multiple days from the present date.

I need to generate two dates, but I need to use the complete date (01/03/01)

$varible1 = present date
$varibel2 = date - 14 days

How might this be accomplished ?



-Danny

 

[jad]

TODAY=`date &quot;+%y %m %d&quot; | nawk '{split(&quot;31,31,28,31,30,31,30,31,31,30,31,30&quot;,month,&quot;,&quot; if ($1 % 4 == 0) {month[3]=29;}; day=$3-<num days>; year=$1; mon=$2; if (day <= 0) {day+=month[$2-0]; mon=$2-1; year=$1-1} printf(&quot;%02d/%02d/%02d&quot;,day,mon,year);}'`
echo $TODAY

woo

i love scripts

note <num days> is the number of days you want to subtract

 

[abovebrd]

jad,

looks very promising

However I am getting an error when I try to use your script.
I replaced <num days> with 14 and this is what happensnawk: Syntax error
at line 1 of program << {split(&quot;31,31,28,31, ... >>
context is
if ($1 % 4 == 0) {month[3]=29;}; day=$3-14 >>> year= <<< $1; mon=$2;
nawk: illegal statement
at line 1 of program << {split(&quot;31,31,28,31, ... >>

Any advise



-Danny

 

[jad]

TODAY=`date &quot;+%y %m %d&quot; | nawk '{split(&quot;31,31,28,31,30,31,30,31,31,30,31,30&quot;,month,&quot;,&quot; if ($1 % 4 == 0) {month[3]=29;}; day=$3-14; year=$1+0; mon=$2+0; if (day <= 0) {day+=month[$2-0]; mon=$2-1; if (mon==0) {year=$1-1; mon=12;}} printf(&quot;%02d/%02d/%02d&quot;,day,mon,year);}'`
echo $TODAY

i got the year slightly wrong anyway ... but the stuff above works (forgot to convert from string to number with +0)

 

[abovebrd]

jad,

That's a beautiful thing.

You deserve a pint of Guiness for that one.

It works wonderful !!!!!!!!!

thank you


-Danny

 

[jad]

if it weren't for the new baby, and wanting to avoid the hangover, i'd take you up on that one

Jon

 

[itsmythg]

TODAY=`date &quot;+%y %m %d&quot; | nawk '{split(&quot;31,31,28,31,30,31,30,31,31,30,31,30&quot;,month,&quot;,&quot; if ($1 % 4 == 0) {month[3]=29;}; day=$3-1; if (day == 0) {day=month[$2-0];} printf(&quot;%02d&quot;,day);}'`
echo $TODAY

This works great but I need to add the Month to this too.

Roxanne

 

[babeo]

Hi Roxanne

The code is just there, try this one:

TODAY=`date &quot;+%y %m %d&quot; | nawk '{split(&quot;31,31,28,31,30,31,30,31,31,30,31,30&quot;,month,&quot;,&quot;
if ($1 % 4 == 0) {month[3]=29;};
day=$3-1;
mon=$2+0;
year=$1+0;[/red]
if (day == 0) {day=month[$2-0];} printf(&quot;%02d/%02d/%02d[/red]&quot;,day,mon, year[/red]);}'`
echo $TODAY

If you don't want the year to be displayed, then just take off the code for the year.
babeo

 

[cfsalmeida]

you can also try this:

env TZ=&quot;$TZ+24&quot; date +%d

for same cases is more simple.

Regards,

Carlos Almeida,

 

[frankj]

Great tip ...

FJ

 

[OraMan]

Month cal is not coming up right.
for Jan, it becomes 00, insted of 12
please help

 

[trunix]

An easy solution to this ....

Set up a cron which runs at five minutes to midnight

date > /tmp/yesterdays_date

When you run your script the next day just cat this file and you have yesterdays date !!!!

It works every time....................

 

[aego]

it would, but what if cron fails for some reason ?