How to add pipe to groovy exec command-line?

Question

I am trying to get information on a specific commit. How do I add a pipe to the command-line?

def getCommitLog(commit){
    def stdout = new ByteArrayOutputStream()
    exec {
        ignoreExitValue true
        workingDir 'my_dir'
        commandLine 'git', 'log', '--decorate', '|', 'grep', commit
        standardOutput = stdout
    }
    def retval = stdout.toString().trim()
    return retval

It throws this error:

fatal: ambiguous argument '|': unknown revision or path not in the working tree.
Use '--' to separate paths from revisions, like this:
'git <command> [<revision>...] -- [<file>...]

Answer 1

Use a subshell: ['bash', '-c', '<entire command>']

exec {
    commandLine = ['bash', '-c', 'find build/ -iname log4j.xml | xargs ls -lh' ]
}

Answer 2

May be you can try changing as below i.e., use list

from:

commandLine 'git', 'log', '--decorate', '|', 'grep', commit

to:

commandLine ['git', 'log', '--decorate', '|', 'grep', 'commit']