How do I interpolate wildcards into a shell command?

Question

I\'m trying to build a Snakemake pipeline, but I\'m confused why filename wildcards work for input and output, but not for shell. For exam

Answer 1

Wildcards are available via {wildcards.XXXX}. source

rule align:
    input: "{sample}.txt"
    output: "{sample}.out"
    shell: "touch {wildcards.sample}.out"