How to get a value from file and store it in a variable? (using shell script)

Question

I have a file as mention below

import org.slf4j.LoggerFactory

class UpdateAvamDb {

        private final def DEFAULT_STALE_BACKUP_HOURS = 1.0

From an another file i want to read this file and get the integer value after DEFAULT_STALE_BACKUP_HOURS into a variable.

I have read about awk but i am not able to do it, please help

Thank you

You could use grep; try searching a bit on this site. There are plenty of examples. — devnull
– devnull, Commented Mar 19, 2014 at 11:39
i tried with grep, there is a problem in using it , i have more than one line in this file which is uses 'DEFAULT_STALE_BACKUP_HOURS' and grep is returning all of them. I read many examples but could not get what i want..so posted a question — user3429026
– user3429026, Commented Mar 19, 2014 at 11:44

shellter · Accepted Answer · 2014-03-19 11:58:52Z

1

echo "import org.slf4j.LoggerFactory
class UpdateAvamDb {
        private final def DEFAULT_STALE_BACKUP_HOURS = 1.0" \
| awk  '/DEFAULT_STALE_BACKUP_HOUR/{print $NF}'

output

1.0

echo "import .... \ | is a quick way to perform a test with your data, rather than put it into a file. The awk code block will perform the same function if you replace the print "..." | with the input filename at the end:

  awk '/..../{print $NF}' myFile
  1.0

And your heading says, store value in variable, so here we go:

 myVar=$(awk '/DEFAULT_STALE_BACKUP_HOUR/{print $NF}')

 echo "myVar=$myVar"
 1.0

AND based on your latest comment NOT to get all values. (I hope you only want the first one)

 myVar=$(awk '/DEFAULT_STALE_BACKUP_HOUR/{print $NF;exit}')

 echo "myVar=$myVar"
 1.0

We exit file processing as soon as we match 'DEFAULT....' and print the value.

Anyway!, awk is reading its input, either from a pipe or the file, and asking "does this line have the pattern "DEFAULT_STALE_BACKUP_HOUR" anywhere inside it?" . When it finds a line with that, it will then print the last field on the line, specfied with $NF. NF is an variable that gets set for each line that is read and means 'Number of Fields'. Adding the $ to the front then "converts" the expression to another common awk idom, in this case $6, which means print the 6th field from the current line.

A good tutorial about awk is at Grymoire's awk tutorial

IHTH

P.S. (The awk code is simple, but fragile because of your question is very specific. It is not a generalized answer. We'd need to see a better question definition to provide a solution that will work for more than just DEFAULT_.... )

edited Mar 19, 2014 at 11:58

answered Mar 19, 2014 at 11:42

shellter

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4 Comments

shellter Over a year ago

@user3429026 : I'm glad to hear it. Please accept my answer by clicking the green arrow you will see when you "hover" your mouse near the vote counts. Good luck.

user3429026 Over a year ago

Hi Shellter, earlier i have used the same awk command but added ^ before 'DEFAULT_STALE_BACKUP_HOUR' so i did not get the output value.awk '/^DEFAULT_STALE_BACKUP_HOUR/{print $NF}' can you explain me the reason

shellter Over a year ago

In awk (and sed), you match a line of input with /matchForMe/. In your example, you are matching for the most basic type, a string. but the /matchForMe/ can be a regular expression (which is the subject of book-length discussions). Your ^ char is a reg-expr symbol that means 'Starting at the beginning of the line'. Note that my original explanation I said that /DEF.../ will match anywhere on the line. Now, with the ^ char you limiting the search to match that word only if it is at the beginning of the line. Any further questions about reg-exps should be posted as new Qs. Good luck.

shellter Over a year ago

And questions are mostly easily answered, pretty much has you have done in your question above. 1. Here is my input data (small sample, simple enough to diagnose the problem, but not pages and pages of irrelavant stuff). 2. Here is my required output from that input. 3. Here is my code, 4. here is my current output. 5. here are my thoughts and question about why it is not working. (This is for the benefit of other readers!). Good luck.

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