CODEWITHSUNDEEP
linuxbashshellawkgrep
Starry
Starry

Reputation: 805

awk after grep: print value when grep returns nothing

I have a question when I use awk and grep to parse log files. The log file contains some strings with figures, e.g.

Amount: 20
Amount: 30.1

And I use grep to parse the lines with keyword "Amount", and then use awk to get the amount and do a sum:

the command is like:

cat mylog.log | grep Amount | awk -F 'Amount: ' '{sum+=$2}END{print sum}'

It works fine for me. However, sometimes the mylog.log file does not contains the keyword 'Amount'. In this case, I want to print 0, but the above awk command will print nothing. How can I make awk print something when grep returns nothing?

Upvotes: 0

Views: 1402

Answers (3)

Ed Morton
Ed Morton

Reputation: 203625

If your line only contains "Amount: 20" then use @fedorqui's solution, but if it's more like "The quick brown fox had Amount: 20 bananas" then use:

awk -F'Amount:' 'NF==2{sum+=$2} END{print sum+0}' file

Upvotes: 2

Avinash Raj
Avinash Raj

Reputation: 174706

Awk one-liner,

awk -F 'Amount: ' '/Amount:/{print "1";sum+=$2}!/Amount:/{print "0"}END{print sum}' file

The above awk command would print the number 1 for the lines which has the string Amount and it prints 0 for the lines which don't have the string Amount. And also if the string Amount is found on a line then it stores the value(column 2) to the sum variable and adds it with any further values. Finally the value of the variable sum is printed at the last.

Example:

$ cat file
Amount: 20
Amount: 30.1
foo bar
adbcksjc
sbcskcbks
cnskncsnc
$ awk -F 'Amount: ' '/Amount:/{print "1";sum+=$2}!/Amount:/{print "0"}END{print sum}' file
1
1
0
0
0
0
50.1

Upvotes: 1

fedorqui
fedorqui

Reputation: 289745

You can use this:

awk '/^Amount/ {amount+=$2} END {print amount+0}' file

With the +0 trick you make it print 0 in case the value is not set.

Explanation

There is no need to grep + awk. awk alone can grep (and many more things!):

  • /^Amount/ {} on lines starting with "Amount", perform what is in {}.
  • amount+=$2 add field 2's value to the counter "amount".
  • END {print amount+0} after processing the whole file, print the value of amount. Doing +0 makes it print 0 if it wasn't set before.

Note also there is no need to set 'Amount' as the field separator. It suffices with the default one (the space).

Test

$ cat a
Amount: 20
Amount: 30.1
$ awk '/^Amount/ {amount+=$2} END {print amount+0}' a
50.1

$ cat b
hello
$ awk '/^Amount/ {amount+=$2} END {print amount+0}' b
0

Upvotes: 5

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