[FIXED] Groovy sh calling docker build is adding newlines to my command

Issue

Hopefully this is a straightforward issue. I have a groovy method I'm calling from within a Jenkinsfile that is supposed to execute a docker build shell command. The line is as follows:

sh "docker build --build-arg \"VERSION=${tag}\" -t \"${project}:${tag}\" ."

However, when I run this from Jenkins, it seems to break this command into newlines, confusing docker:

17:26:05.151  docker build --build-arg "VERSION=<tag>
17:26:05.151  " -t "<project>:<tag>
17:26:05.151  " .
17:26:05.451  invalid argument "<project>:<tag>\n" for "-t, --tag" flag: invalid reference format
17:26:05.451  See 'docker build --help'.

The double quotes around the variables were necessary to get the full command in in some form. Without them, the output cuts off, like this:

17:17:24.368  ++ docker build --build-arg VERSION=<tag>
17:17:24.368  "docker build" requires exactly 1 argument.

Something is definitely wrong with how I'm translating bash to groovy, but I'm not sure what.

Solution

Consider the following:

def tag = "testing_tag\n"
def project="test_proj"

node {

    echo "docker build --build-arg \"VERSION= " + 
         tag + 
         "\" -t \"${project}:" + 
         tag + "\" ."
}

Will give you exactly what you have:

docker build --build-arg "VERSION=tag
" -t "project:tag
" .

You can get rid of any newline characters using .replace("\n", "" )

def tag = "tag\n"
def project="project"

node {

    echo "docker build --build-arg \"VERSION=" + 
         tag.replace("\n", "" ).trim() + 
         "\" -t \"${project}:" + 
         tag.replace("\n", "" ).trim() + "\" ."
}

---

A better option would be replacing all newline characters:

echo "docker build --build-arg \"VERSION=${tag}\" -t \"${project}:${tag}\" .".replace("\n", "" ).trim()

---

Now you just need to substitute echo with sh

def tag = "tag\n"
def project="project"

node {
    def command = "docker build --build-arg \"VERSION=${tag}\" -t \"${project}:${tag}\" .".replace("\n", "" ).trim()
    echo command
    sh command
}

This example replaces every newline character, regardless if it's a variable coming from Jenkins (in my case) or not. Just adapt for your needs.

Answered By - agentsmith
Answer Checked By - Mary Flores (JavaFixing Volunteer)