Question

I am curious if there’s an easy solution for this seemingly complex task:

Say I have this file:

lineone
linetwo
linethree
linefour

lineone
linetwo
linethree
linefour

lineone
lineone
lineone
linetwo
linethree
linefour

Is there a simple way you can think of to get this result:

lineone[1]
linetwo[1]
linethree[1]
linefour[1]

lineone[2]
linetwo[2]
linethree[2]
linefour[2]

lineone[3]
lineone[4]
lineone[5]
linetwo[3]
linethree[3]
linefour[3]

To put it in words, is there a simple bash algorithm that would let me number each line in the order of it’s occurence in a file? I cannot figure out a way to do this without some complex solution involving additional storage, and the usual commands I use for line replacement are useless here. sed would just replace all occuring lines with the same value, and the string replace ( ${string/substring/replace} ) would not help me since it will not maintain the order of the lines.

Much appreciated.

Answer 1

The following awk command works by keeping an array of lines and their counts.

awk '{if($0~/./){a[$0]++;print $0"["a[$0]"]";} else print}' file

Example:

$ cat file
lineone
linetwo
linethree
linefour

lineone
linetwo
linethree
linefour

lineone
linetwo
linethree
linefour

lineone
lineone
lineone
linetwo
linethree
linetwo

$ awk '{if($0~/./){a[$0]++;print $0"["a[$0]"]";} else print}' file
lineone[1]
linetwo[1]
linethree[1]
linefour[1]

lineone[2]
linetwo[2]
linethree[2]
linefour[2]

lineone[3]
linetwo[3]
linethree[3]
linefour[3]

lineone[4]
lineone[5]
lineone[6]
linetwo[4]
linethree[4]
linetwo[5]