Jenkins pipeline sh does not seem to respect pipe in shell command - jenkins

Question

I am using a Jenkinsfile in a pipeline on version 2.32.2.
For various reasons I want to extract the version string from the pom. I was hoping I wouldn't have to add the maven help plugin and use evaluate.
I quickly came up with a little sed expression to get it out of the pom which uses pipes and works on the commandline in the jenkins workspace on the executor.
$ sed -n '/<version>/,/<version/p' pom.xml | head -1 | sed 's/[[:blank:]]*<\/*version>//g'
1.0.0-SNAPSHOT
It could probably be optimized, but I want to understand why the pipeline seems to be failing on piped sh commands. I've played with various string formats and am currently using a dollar slashy string.
The pipeline step looks like the following to allow for easy output of the command string:
script {
def ver_script = $/sed -n '/<version>/,/<version/p' pom.xml | head -1 | sed 's/[[:blank:]]*<\/*version>//g'/$
echo "${ver_script}"
POM_VERSION = sh(script: "${ver_script}", returnStdout: true)
echo "${POM_VERSION}"
}
When run in the jenkins pipeline I get the following console output where it seems to be separating the piped commands into separate commands:
[Pipeline] script
[Pipeline] {
[Pipeline] echo
sed -n '/<version>/,/<version/p' pom.xml | head -1 | sed 's/[[:blank:]]*<\/*version>//g'
[Pipeline] sh
[FRA-198-versioned-artifacts-44SD6DBQOGOI54UEF7NYE4ECARE7RMF7VQYXDPBVFOHS5CMSTFLA] Running shell script
+ sed -n /<version>/,/<version/p pom.xml
+ head -1
+ sed s/[[:blank:]]*<\/*version>//g
sed: couldn't write 89 items to stdout: Broken pipe
[Pipeline] }
[Pipeline] // script
Any guidance out there on how to properly use piped commands in a jenkinsfile ?

Answer 1

I finally put some thought into it and realized that pipe subshells are probably causing the issue. I know some of the evils of eval but I ended up wrappping this in an eval:
script {
def ver_script = $/eval "sed -n '/<version>/,/<version/p' pom.xml | head -1 | sed 's/[[:blank:]]*<\/*version>//g'"/$
echo "${ver_script}"
POM_VERSION = sh(script: "${ver_script}", returnStdout: true)
echo "${POM_VERSION}"
}

Answer 2

I know this kind of late answer, but whoever you who needs the solution without eval you can use /bin/bash -c "script" to make pipe works
script {
POM_VERSION = sh(script: "/bin/bash -c 'sed -n \'/<version>/,/<version/p\' pom.xml | head -1 | sed \'s/[[:blank:]]*<\/*version>//g\'\''", returnStdout: true)
echo "${POM_VERSION}"
}
The only problem with this method is hellish escape yet this way the subshell of pipe will be handled by our boy /bin/bash -c

Answer 3

If your environment allows it, I've found a simple solution to this problem to be to place your script containing pipes into a file, and then run that with sh, like so:
script.sh:
#!/bin/sh
kubectl exec --container bla -i $(kubectl get pods | awk '/foo-/{ print $1 }') -- php /code/dostuff
Jenkinsfile:
stage('Run script with pipes') {
steps {
sh "./script.sh"
}
}

Answer 4

The pipeline-utility-steps plugin nowadays includes a readMavenPom step, which allows to access the version as follows:
version = readMavenPom.getVersion()

Answer 5

So nothing detailed above worked for me using the scripted Jenkinsfile syntax with Groovy. I was able to get it working, however. The type of quotations you use are important. In the example below, I am trying to fetch the latest git tag from GitHub.
...
stage("Get latest git tag") {
if (env.CHANGE_BRANCH == 'master') {
sh 'git fetch --tags'
TAGGED_COMMIT = sh(script: 'git rev-list --branches=master --tags --max-count=1', returnStdout: true).trim()
LATEST_TAG = sh(script: 'git describe --abbrev=0 --tags ${TAGGED_COMMIT}', returnStdout: true).trim()
VERSION_NUMBER = sh(script: "echo ${LATEST_TAG} | cut -d 'v' -f 2", returnStdout: true).trim()
echo "VERSION_NUMBER: ${VERSION_NUMBER}"
sh 'echo "VERSION_NUMBER: ${VERSION_NUMBER}"'
}
}
...
Notice how the shell execution to assign LATEST_TAG works as expected (assigning the variable to v2.1.0). If we were to try the same thing (with single quotes) to assign VERSION_NUMBER, it would NOT work - the pipe messes everything up. Instead, we wrap the script in double quotes.
The first echo prints VERSION_NUMBER: 2.1.0 but the second prints VERSION_NUMBER:. If you want VERSION_NUMBER to be available in the shell commands, you have to assign the output of the shell command to env.VERSION_NUMBER as shown below:
...
stage("Get latest git tag") {
if (env.CHANGE_BRANCH == 'master') {
sh 'git fetch --tags'
TAGGED_COMMIT = sh(script: 'git rev-list --branches=master --tags --max-count=1', returnStdout: true).trim()
LATEST_TAG = sh(script: 'git describe --abbrev=0 --tags ${TAGGED_COMMIT}', returnStdout: true).trim()
env.VERSION_NUMBER = sh(script: "echo ${LATEST_TAG} | cut -d 'v' -f 2", returnStdout: true).trim()
echo "VERSION_NUMBER: ${VERSION_NUMBER}"
sh 'echo "VERSION_NUMBER: ${VERSION_NUMBER}"'
}
}
...
The first echo prints VERSION_NUMBER: 2.1.0 and the second prints VERSION_NUMBER: 2.1.0.

Answer 6

I am also struggling with the usage of pipe inside my jenkins pipeline but as a side note, if you want a simple way to extract the version of a maven pom, here's a very clean one I found in another post and that I'm using :
stage('Preparation') {
version = getVersion()
print "version : " + version
}
def getVersion() {
def matcher = readFile('pom.xml') =~ '<version>(.+)</version>'
matcher ? matcher[0][1] : null
}
gives you :
[Pipeline] echo
releaseVersion : 0.1.24
[Pipeline] sh