====== sed ======

===== Replace the \n with values =====
Refer
  - https://blog.csdn.net/mfkjq/article/details/80377114
==== Use test command ====
  gsed ":a;N;s/\n/,/g;ta"
Or
  gsed ":d;N;s/\n/,/g;td"
It means it will jump to the tag :a or :d, if one time failed, then it will break.

==== Use branch command ====
  gsed ":a;N;s/\n/,/g;ba"
Or
  gsed ":d;N;s/\n/,/g;bd"

==== delete the redundant empty lines ====
Refer
  - http://kodango.com/sed-and-awk-notes-part-5

  sed '/^$/{N;/^\n$/D}'

E.g. Remove all the redundant empty lines in the Java source code

  find app/src/ -iname "*.java" -exec gsed -i '/^$/{N;/^\n$/D}' {} +
  
==== Combine every 3 lines into one line ====
  sed 'N;N;s/\n/ /g'
  
==== Calculate the number ====
  cat crashlist_googleplay_20181012.txt|grep -v "^$"|grep -A 2 "^in"|grep -v "-"|gsed "N;N;s/\n/ /g"|awk '{sum += $4 } END { print sum }'