How to grep number of unique occurrences

Question

I understand that grep -c string can be used to count the occurrences of a given string. What I would like to do is count the number of unique occurrences when

Answer 1

In general, if you want to grep and also keep track of results, it is best to use awk since it performs such things in a clear manner with a very simple syntax.

So for your given file I would use:

$ awk -F= '/string=/ {count[$2]++} END {for (i in count) print i, count[i]}' file
value1 3
value2 2
value3 1

What is this doing?

• -F=
  set the field separator to =, so that we can compute the right and left part of it.
• /string=/ {count[$2]++}
  when the pattern "string=" is found, check it! This uses an array count[] to keep track on the times the second field has appeared so far.
• END {for (i in count) print i, count[i]}
  at the end, loop through the results and print them.