使用Groovy获取进程的PID

String getProcessIdFor(String program) {
    def buffer = new StringBuffer()

    Process commandOne = 'ps -A'.execute()
    Process commandTwo = "grep -m1 '${program}'".execute()
    Process commandThree = "awk '{print \$1}'".execute()

    Process process = commandOne | commandTwo | commandThree
    process.waitForProcessOutput(buffer,buffer)

    return buffer.toString()
}

但这给了我：

Exception in thread "Thread-1" groovy.lang.GroovyRuntimeException: exception while reading process stream
awk: Syntax error at source line 1
at org.codehaus.groovy.runtime.ProcessGroovymethods$3.run(ProcessGroovymethods.java:402)
context is
at java.lang.Thread.run(Thread.java:745)
 >>> ' <<< 
missing }
Caused by: java.io.IOException: Stream closed
awk: bailing out at source line 1
at java.lang.ProcessBuilder$NullOutputStream.write(ProcessBuilder.java:434)
at java.io.outputStream.write(OutputStream.java:116)
at java.io.bufferedoutputstream.write(bufferedoutputstream.java:122)
at java.io.bufferedoutputstream.write(bufferedoutputstream.java:122)
at org.codehaus.groovy.runtime.ProcessGroovymethods$3.run(ProcessGroovymethods.java:399)
... 1 more

Process finished with exit @R_215_6756@

看起来它在awk命令上挣扎,但我似乎无法弄清楚我哪里出错了.有任何想法吗？