Awk/Unix group by

by 
$ awk -F, 'NR>1{arr[$1]++}END{for (a in arr) print a, arr[a]}' file.txt
joe 1
jim 1
mike 3
bob 2

EXPLANATIONS

  • -F, splits on ,
  • NR>1 treat lines after line 1
  • arr[$1]++ increment array arr (split with ,) with first column as key
  • END{} block is executed at the end of processing the file
  • for (a in arr) iterating over arr with a key
  • print a print key , arr[a] array with a key

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