I know this is an old question, but i had to this myself recently. I figure this would help someone else looking to do the same. Here's a Groovy script that will read a given job's progressiveText URL. The code is written in such a way that it should be plug and play. Make sure to set the jenkinsBase and jobName first. The approach is no different to what has already been mentioned.
Here's a short set of instructions on how to use this: (1) Configure downstream job so that anonymous users hasRead and ViewStatus rights. (2) In the upstream job, create a Trigger/call builds on other projects step that will call the downstream job. (3) Do not check the "Block until the triggered projects finish their builds. (4) Right after that step, create an Execute Groovy script step and paste the following code:
def jenkinsBase = // Set to Jenkins base URL here
def jobName = // Set to jenkins job name
def jobNumber = 'lastBuild' // Tail last build
def address = null
def response = null
def start = 0 // Start at offset 0
def cont = true // This semaphore holds the value of X-More-Data header value
try {
while (cont == true) { // Loop while X-More-Data value is equal to true
address = "${jenkinsBase}/job/${jobName}/${jobNumber}/logText/progressiveText?start=${start}"
def urlInfo = address.toURL()
response = urlInfo.openConnection()
if (response.getResponseCode() != 200) {
throw new Exception("Unable to connect to " + address) // Throw an exception to get out of loop if response is anything but 200
}
if (start != response.getHeaderField('X-Text-Size')) { // Print content if the starting offset is not equal the value of X-Text-Size header
response.getInputStream().getText().eachLine { line ->
println(line)
}
}
start = response.getHeaderField('X-Text-Size') // Set new start offset to next byte
cont = response.getHeaderField('X-More-Data') // Set semaphore to value of X-More-Data field. If this is anything but true, we will fall out of while loop
sleep(3000) // wait for 3 seconds
}
}
catch (Exception ex) {
println (ex.getMessage())
}
This script can be further improved by programatically getting the downstream job number.
There is also a Python version of this approach here.