[SOLVED] Using awk to do calculation inside a text file

xisan · 04-25-2017, 03:47 PM

Hi,

I'm very new in Linux operating system. I've started looking at different types scripting and trying to manipulate one of the large text files that I'm using to run a simulation of coastal flooding. Following is the text file:

Code:

FileVersion      = 1.03
Filetype         = meteo_on_curvilinear_grid
 TIME = 0 hours since 1900-01-01 12:00:00 +00:00
 -6.855  -6.828  -6.801  -6.774  -6.747  -6.719  -6.691  -6.663  -6.634  -6.606  -6.577  -6.548  -6.519  -6.489  
 TIME = 0 hours since 1900-01-01 12:00:00 +00:00
 -6.855  -6.828  -6.801  -6.774  -6.747  -6.719  -6.691  -6.663  -6.634  -6.606  -6.577  -6.548  -6.519  -6.489  
 TIME = 0 hours since 1900-01-01 12:00:00 +00:00
 -6.855  -6.828  -6.801  -6.774  -6.747  -6.719  -6.691  -6.663  -6.634  -6.606  -6.577  -6.548  -6.519  -6.489
TIME = 0 hours since 1900-01-01 12:00:00 +00:00
 -6.855  -6.828  -6.801  -6.774  -6.747  -6.719  -6.691  -6.663  -6.634  -6.606  -6.577  -6.548  -6.519  -6.489

The file is very large; around 78 MB. I just shortened it to the first few lines. If you notice carefully, all the times are showing 0 hours and for 1900-01-01 12:00:00 +00:00 time periods. I wanted all the 1900-01-01 12:00:00 +00:00 to change in to 2016-10-03 12:00:00 +00:00 . And I did this by using

Code:

sed -i 's/1900-01-01/2016-10-03/g' file.txt

but I also want to change all the time which are showing 0 hours

Code:

TIME = 0 hours since

to change 6 hourly intervals so that it becomes like this:

Code:

TIME = 0 hours since 
TIME = 6 hours since
TIME = 12 hours since
TIME = 18 hours since

The output that I'm trying to get finally is something like this:

Code:

FileVersion      = 1.03
Filetype         = meteo_on_curvilinear_grid
 TIME = 0 hours since 2016-10-03 12:00:00 +00:00
 -6.855  -6.828  -6.801  -6.774  -6.747  -6.719  -6.691  -6.663  -6.634  -6.606  -6.577  -6.548  -6.519  -6.489  
 TIME = 6 hours since 2016-10-03 12:00:00 +00:00
 -6.855  -6.828  -6.801  -6.774  -6.747  -6.719  -6.691  -6.663  -6.634  -6.606  -6.577  -6.548  -6.519  -6.489  
 TIME = 12 hours since 2016-10-03 12:00:00 +00:00
 -6.855  -6.828  -6.801  -6.774  -6.747  -6.719  -6.691  -6.663  -6.634  -6.606  -6.577  -6.548  -6.519  -6.489
TIME = 18 hours since 2016-10-03 12:00:00 +00:00
 -6.855  -6.828  -6.801  -6.774  -6.747  -6.719  -6.691  -6.663  -6.634  -6.606  -6.577  -6.548  -6.519  -6.489

Is it possible to conduct both the operations by using a single loop combining sed and awk operations. Can anyone suggest me which options would be best here? That'd be very helpful for my work.

Thanks in advance.

MadeInGermany · 04-25-2017, 04:35 PM

You need a single loop.
sed does not handle variables, so this one is better for awk:

Code:

awk 'BEGIN {t=0} ($1=="TIME" && $2=="=" && $3=="0" && $6=="1900-01-01") {$3=t; t+=6; $6="2016-10-03"} {print}' file.txt

If this looks good, redirect its output to a new(!) file.
As a last step you can copy or move the new file back to the original file.

xisan · 04-25-2017, 06:46 PM

That worked perfectly, thanks!