gongzhitaao · October 23, 2013 02:43
diff --git a/sed-one-liner b/sed-one-liner
 # input:
 # 1 1
 # 2 2
 # 3 3
 # 4 4
 # 5 5
 # 6 6
 # 7 7
 # output:
 # 1
 # 4
 # 7
 sed '1~3 !d;s/^\(.*\)\s\+\1/\1/' file
	# input:
	# 1 1
	# 2 2
	# 3 3
	# 4 4
	# 5 5
	# 6 6
	# 7 7
	# output:
	# 1
	# 4
	# 7
	sed '1~3 !d;s/^\(.*\)\s\+\1/\1/' file