How can I walk through two files simultaneously in Perl?
- by Alex Reynolds
I have two text files that contain columnar data of the variety position-value, sorted by position.
Here is an example of the first file (file A):
100 1
101 1
102 0
103 2
104 1
...
Here is an example of the second file (B):
20 0
21 0
...
100 2
101 1
192 3
193 1
...
Instead of reading one of the two files into a hash table, which is prohibitive due to memory constraints, what I would like to do is walk through two files simultaneously, in a stepwise fashion.
What this means is that I would like to stream through lines of either A or B and compare position values.
If the two positions are equal, then I perform a calculation on the values associated with that position.
Otherwise, if the positions are not equal, I move through lines of file A or file B until the positions are equal (when I again perform my calculation) or I reach EOF of both files.
Is there a way to do this in Perl?
