workflow rerun again and again

[wangjiawen2013]

Hi, here is a toy code I wrote (test.smk):

rule all:
input:
"/home/wangjw/data/work/flask/b.txt"

rule copy1:
input:
file = directory("/home/wangjw/data/work/flask")
output:
file = "data1/a.txt"
shell:
"cp {input.file}/a.txt {output.file}"

rule copy2:
input:
file = "data1/a.txt"
output:
file = "/home/wangjw/data/work/flask/b.txt"
shell:
"cp {input.file} {output.file}"

then I run snakemake -j 1 -s test.smk, the workflow will run again each time I perform "snakemake -j 1 -s test.smk", although all the files have been created.