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bashshellgroovyprocess
Les Hazlewood
Les Hazlewood

Reputation: 19567

Using groovy, how do you pipe multiple shell commands?

Using Groovy and it's java.lang.Process support, how do I pipe multiple shell commands together?

Consider this bash command (and assume your username is foo):

ps aux | grep ' foo' | awk '{print $1}'

This will print out usernames - one line for some processes related to your user account.

Using Groovy, the ProcessGroovyMethods documentation and code says I should be able to do this to achieve the same result:

def p = "ps aux".execute() | "grep ' foo'".execute() | "awk '{print $1}'".execute()
p.waitFor()
println p.text

However, I can't get any text output for anything other than this:

def p = "ps aux".execute()
p.waitFor()
println p.text

As soon as I start piping, the println does not print out any anything.

Thoughts?

Upvotes: 23

Views: 36541

Answers (4)

Here_2_learn
Here_2_learn

Reputation: 5451

This has worked for me

def command = '''
    ps aux | grep bash | awk '{print $1}'
'''
def proc = ['bash', '-c', command].execute()
proc.waitFor()
println proc.text

If you want to run multiple commands, you can add it in the command.

def command = '''
    ls -ltr
    cat secret
'''
def proc = ['bash', '-c', command].execute()
proc.waitFor()
println proc.text

Upvotes: 8

Gilad Baruchian
Gilad Baruchian

Reputation: 980

If you want it async I recommend 

 proc.consumeProcessOutputStream(new LineOrientedOutputStream() {
        @Override
        protected void processLine(String line) throws IOException {
           println line
        }
    }
    );

Upvotes: 0

Jérémie B
Jérémie B

Reputation: 11032

This works for me :

def p = 'ps aux'.execute() | 'grep foo'.execute() | ['awk', '{ print $1 }'].execute()
p.waitFor()
println p.text

for an unknown reason, the parameters of awk can't be send with only one string (i don't know why! maybe bash is quoting something differently). If you dump with your command the error stream, you'll see error relative to the compilation of the awk script.

Edit : In fact,

  1. "-string-".execute() delegate to Runtime.getRuntime().exec(-string-)
  2. It's bash job to handle arguments containing spaces with ' or ". Runtime.exec or the OS are not aware of the quotes
  3. Executing "grep ' foo'".execute() execute the command grep, with ' as the first parameters, and foo' as the second one : it's not valid. the same for awk

Upvotes: 35

tim_yates
tim_yates

Reputation: 171194

You can do this to just let the shell sort it out:

// slash string at the end so we don't need to escape ' or $
def p = ['/bin/bash', '-c', /ps aux | grep ' foo' | awk '{print $1}'/].execute()
p.waitFor()
println p.text

Upvotes: 17

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