Groovy File() not reporting correct size / length - groovy

Question

I have a Jenkins post build Groovy script running out of the "Post build task plugin". From the same plugin, immediately before running the Groovy script, I check for the existence of the file and its size. The log shows:
09:14:53 -rw-r--r-- 1 aaa users 978243 Nov 4 08:53 /jk/workspace/xxxx/output/delta.txt
09:14:53 cppcheck.groovy: Checking build result: SUCCESS
09:14:53 cppcheck.groovy: workspace = /jk/workspace/xxxx
09:14:53 cppcheck.groovy: delta = /jk/workspace/xxxx/output/delta.txt
09:14:53 cppcheck.groovy: delta.txt length = 0
The groovy script is as follows:
import hudson.model.*
def build = Thread.currentThread().executable
def result = build.getResult()
println("cppcheck.groovy: Checking build result: " + result.toString())
if (result.isBetterOrEqualTo(hudson.model.Result.SUCCESS)) {
def workspace = build.getEnvVars()["WORKSPACE"]
def delta = workspace + "/output/delta.txt"
println("cppcheck.groovy: workspace = " + workspace)
println("cppcheck.groovy: delta = " + delta)
def f = new File(delta)
println("cppcheck.groovy: delta.txt length = " + f.length())
if (f.length() > 0) {
build.setResult(hudson.model.Result.UNSTABLE)
}
}
What am I doing wrong here?
Update: There seems to be some scepticism that the file exists and that there is some sort of race condition. To put your minds at rest, let's rule that out. I have modified the build to execute the same ls -l command after it runs the groovy script, to prove the file does exist and that this problem is ultimately Groovy not being able to open the file. I also added the file exists() check to the above Groovy script, which as I suspected it would, reports the file doesn't exist. I don't dispute that Groovy thinks the file doesn't exist. What I am trying to work out is why?
10:31:39 [xxxx] $ /bin/sh -xe /tmp/hudson8964729240493636268.sh
10:31:39 + ls -l /jk/workspace/xxxx/output/delta.txt
10:31:39 -rw-r--r-- 1 aaa users 978243 Nov 4 08:53 /jk/workspace/xxxx/output/delta.txt
10:31:40 cppcheck.groovy: Checking build result: SUCCESS
10:31:40 cppcheck.groovy: workspace = /jk/workspace/xxxx
10:31:40 cppcheck.groovy: delta = /jk/workspace/xxxx/output/delta.txt
10:31:40 cppcheck.groovy: delta.txt length = 0
10:31:40 cppcheck.groovy: delta.txt exists = false
10:31:40 [xxxx] $ /bin/sh -xe /tmp/hudson8007562636561507409.sh
10:31:40 + ls -l /jk/workspace/xxxx/output/delta.txt
10:31:40 -rw-r--r-- 1 aaa users 978243 Nov 4 08:53 /jk/workspace/xxxx/output/delta.txt
Also, notice the timestamp on said file, is still 08:53 when it was created.

Answer 1

I suspected that the Groovy script was running on the build master as opposed to the build node that this particular build was running on. I added some debug to print the hostname for which the Groovy script was running and sure enough it wasn't the same host that the shell variant of the script was running.