matchtable

what is this?

matchtable reads lines from files and generates a map indicating which lines are present in which files. This is similar to the standard Unix utility comm, except that it accepts any number of files at the input.

demo

$ cat testdata.sh
#!/bin/sh

seq 1 3 > A
seq 2 4 > B
seq 3 5 > C
seq 4 5 > D
seq 5 5 > E

./matchtable [A-E] | column -t


$ ./testdata.sh
ITEM  A  B  C  D  E
1     X  -  -  -  -
2     X  X  -  -  -
3     X  X  X  -  -
4     -  X  X  X  -
5     -  -  X  X  X

options

$ ./matchtable -h
Usage of ./matchtable:
  -no-value string
    	string used to indicate an item was NOT present in a column (default "-")
  -separator string
    	string used to separate rendered columns in the output (default " ")
  -sort
    	sort the superset of items lexicographically (default true)
  -yes-value string
    	string used to indicate an item was present in a column (default "X")

original use case

The first use case for matchtable was determining where AWS security groups were used, as they can be referenced in an ever-expanding variety of places, including but very likely not limited to the below:

• security group rules
• EC2 instances
• elastic network interfaces
• RDS database security groups
• RDS instances
• RDS clusters
• VPC endpoints
• Elasticache clusters
• Lambda functions
• Fargate clusters

future improvements

• column aliases
• improved memory efficiency