Question

I have had problems with that the Exec task in gradle have problems with the up-to-date check if the output files is captured from standardOutput.

I have tried to simplify the example as much as possible:

task printToOutputFile(type: Exec) {
    inputs.file file("file1") // not relevant for this example
    outputs.file file("file2")

    commandLine = ["echo", "1234"]
    standardOutput = new FileOutputStream("file2")
}

When rerunning this task I expect it to be UP-TO-DATE but it is not.

How can I make the UP-TO-DATE check work when using the standardOutput as outputs?

What I have tried:
Closing and/or Flushing the stream in an doLast block.

Answer 1

the problem is, that the line

standardOutput = new FileOutputStream("file2")

changes the lastModified attribute of file2. To get the up-to-date check working, you have to move this assignment to the execution phase. You can do this by putting this assignment in a doFirst block. The following snippet should do the trick:

task printToOutputFile(type: Exec) {
    inputs.file file("file1") // not relevant for this example
    outputs.file file("file2")

    commandLine = ["echo", "1234"]

    doFirst{
        standardOutput = new FileOutputStream("file2")
    }
}

cheers,

René