I am a beginner in script writing, i tried to do the following
I have a set of files sorted by date in the format YYMMDD.s and .x and .r
I need to concatenate a header file to these sets of files so I used the following code
echo "enter Swath number"
read s
echo "please enter first date and MMDD press ENTER"
read i
echo "please enter last date and MMDD press ENTER"
read j
for((i; i <= j; i++))
do
cat NJSC_Alam_Ph1_Blk1_3D_HDR_S /ud/SPECSDATA/Final_SPS/Alam3D/Swath_${s}/08${i}.s > /ud/SPECSDATA/Final_SPS/Alam3D/Swath_${s}/08${i}_Final.s
cat NJSC_Alam_Ph1_Blk1_3D_HDR_R /ud/SPECSDATA/Final_SPS/Alam3D/Swath_${s}/08${i}.r > /ud/SPECSDATA/Final_SPS/Alam3D/Swath_${s}/08${i}_Final.r
cat NJSC_Alam_Ph1_Blk1_3D_HDR_X /ud/SPECSDATA/Final_SPS/Alam3D/Swath_${s}/08${i}.x > /ud/SPECSDATA/Final_SPS/Alam3D/Swath_${s}/08${i}_Final.x
done
I expect it to concatenate the files based on the user input.
I have 2 problems, the first on is that it doesn't do this for example if I enter the value for i and j to be 0530 and 0531 for 30 and 31 of May it searches for a file named 08345 instead of 080530.
the other problem is how can i make the script to work for 2 different months? like I have the first file as 300508 and last file as 050608, the loop is not going o work there
Problem number 1 is you're mixing date math with integer math. You cannot add 1 to your "0530" and expect to get the next day. For example, there is no integer "0530". There is an integer "530", however, and if you add 1 to it you will get "531". ...NOT the "0531" that you need. And, as you mentioned, adding 1 to that will not get you into June.
When you do your comparison, you can test for your end condition in either of two ways:
If the current date == the end date (string comparison)
If the current iterations number of seconds since the epoch is less than or equal to the end date's number of seconds since the epoch.
Also, here's a couple of more gotchas you need to be aware of. If you do your date math using "number of seconds since the Epoch",
You may want your first date to actually be midnight of the first date- that is, the 0'th second of that day.
You may want your second date to actually be 23:59:59 on that day.
This is because if you do your "begin <= end" comparison, you may be comparing 3pm on the end day to 2pm on the end day and that iteration of the script will not run.
I mention that because it's convenient to actually do the date math by:
Convert the first date to the number of seconds since the epoch
Increment the date by adding 86,400 (the number of seconds in a day) to the date for each iteration.
You also must be aware of when the year changes. Don't forget you may be comparing dates in January to dates in December.
-mschwage
thank you for the reply, I get what you want to say fine, just one request:
what is the script command to identify a date variable? is there a variable called date?
I tried something like date i, and dim i as date but it didn't work.
I also tried "date -d ${i} +"%y%m%d"" but it said that i is not a command