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Calling external process from Groovy/Java gives unexpected result

From Groovy/Java I try to execute following command: cmd /c echo mytext.

import java.nio.charset.Charset

println(Charset.defaultCharset().displayName()) //returns windows-1250
//in console chcp returns 852

def arg = "/c echo mytext"
def pb = new ProcessBuilder("cmd", arg)
def proc = pb.start()

def stdInput = new BufferedReader(new InputStreamReader(proc.getInputStream(), "CP852"))
def stdError = new BufferedReader(new InputStreamReader(proc.getErrorStream(), "CP852"))

def line = null
println("Here is the standard output of: cmd " + arg)
while ((line = stdInput.readLine()) != null) {
    println(line)
}

println("Here is the standard error of the command (if any):")
while ((line = stdError.readLine()) != null) {
    println(line)
}

Groovy: 2.4.21, 3.0.9

Java: zulu11.50.19-ca-fx-jdk11.0.12-win_x64

The result is mytext" (including ending double quote). I cannot figure out why the double qoute is there. Can anybody help to explain me why is it there?

Thank you.

Answer

in short: ProcessBuilder will wrap each argument that contains spaces with double quotes

so, ProcessBuilder("cmd", "/c echo mytext") actually runs cmd "/c echo mytext"

try this command in command prompt:

c:> cmd "/c echo mytext"
mytext"

^^^ that’s exactly what you have in your result

question why cmd interprets arguments this way must be addressed to microsoft – maybe there is a logical explanation

however echo is not parsing arguments and outputs argument line as is

c:> echo "my text"
"my text"

c:> echo my text
my text

means that correct answer for echo my text: ProcessBuilder("cmd", "/c", "echo my text")


let me suggest a groovy variant for your code:

def out = {s-> print(s)} as Appendable
def err = {s-> print(s)} as Appendable

def command = ['cmd', '/c', 'echo my text']
def proc = command.execute()

proc.waitForProcessOutput(out,err)
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