Capture and convert the output of command into csv file in groovy

I have below code in groovy which is providing 2 different output. I want to take the first row values one by one from command1 output and substitute in command2 as variable in loop.

import java.text.SimpleDateFormat
import java.util.*
import java.text.DateFormat

ANALYSIS_HOME="/jenkins/analysis"
pipeline {
    agent { label 'analysis && linux' }

    stages {
        stage('First step') {
            steps {
                script {
                    withCredentials([[$class: 'UsernamePasswordMultiBinding', credentialsId: 'ANLYSIS', usernameVariable: 'USERNAME', passwordVariable: 'PASSWORD']]) {

                        def projectsList = sh(script: "${ANALYSIS_HOME}/bin/cov-manage-im --url https://example.com/ --on-new-cert trust --user ${USERNAME} --password ${PASSWORD} --mode projects --show --fields project,creation-date,last-modified-date", returnStdout: true)
                        def streamsList = sh(script: "${ANALYSIS_HOME}/bin/cov-manage-im --url https://example.com/ --on-new-cert trust --user ${USERNAME} --password ${PASSWORD} --mode streams --show --fields stream,expiration,primary-project", returnStdout: true)

                        def projectsCSV = "${ANALYSIS_HOME}/projects_output.csv"
                        def streamsCSV = "${ANALYSIS_HOME}/streams_output.csv"

                        writeFile(file: projectsCSV, text: projectsList)
                        writeFile(file: streamsCSV, text: streamsList)
                        
                        println "CSV files have been created: ${projectsCSV} and ${streamsCSV}"
                    }
                }
            }
        }
    }
}

Below is the command output:-

Project,Creation Date,Last Modified Date
A,2022-10-26T12:22:50.191+08:00,2022-10-26T12:22:50.191+08:00
B,2024-05-14T18:06:29.835+08:00,2024-05-14T18:06:29.835+08:00
C,2024-05-20T16:47:27.400+08:00,2024-05-20T16:47:27.400+08:00
D,2024-05-23T16:55:18.828+08:00,2024-05-23T16:55:18.828+08:00
E,2022-08-30T15:11:38.953+08:00,2022-08-30T15:11:38.953+08:00
F,2024-08-13T18:38:59.696+08:00,2024-08-13T18:38:59.696+08:00


Stream,Expiration,Primary Project
A,disabled,A
G,disabled,A
B,disabled,A
C,disabled,D
E,disabled,D
F,disabled,D
E,disabled,D

How can I send the row1 output from command1 one by one in loop to second command and save second command loop output in one single file by concatinating all loop output.

Modify your script to write the projectsList and streamsList outputs into a file

import java.text.SimpleDateFormat
import java.util.*
import java.text.DateFormat

ANALYSIS_HOME="/jenkins/analysis"
pipeline {
    agent { label 'analysis && linux' }

    stages {
        stage('First step') {
            steps {
                script {
                    withCredentials([[$class: 'UsernamePasswordMultiBinding', credentialsId: 'ANLYSIS', usernameVariable: 'USERNAME', passwordVariable: 'PASSWORD']]) {

                        def projectsList = sh(script: "${ANALYSIS_HOME}/bin/cov-manage-im --url https://example.com/ --on-new-cert trust --user ${USERNAME} --password ${PASSWORD} --mode projects --show --fields project,creation-date,last-modified-date", returnStdout: true)
                        def streamsList = sh(script: "${ANALYSIS_HOME}/bin/cov-manage-im --url https://example.com/ --on-new-cert trust --user ${USERNAME} --password ${PASSWORD} --mode streams --show --fields stream,expiration,primary-project", returnStdout: true)

                        def projectsCSV = "${ANALYSIS_HOME}/projects_output.csv"
                        def streamsCSV = "${ANALYSIS_HOME}/streams_output.csv"

                        writeFile(file: projectsCSV, text: projectsList)
                        writeFile(file: streamsCSV, text: streamsList)
                        
                        println "CSV files have been created: ${projectsCSV} and ${streamsCSV}"
                    }
                }
            }
        }
    }
}

you will have two CSV files (projects_output.csv and streams_output.csv) saved in the specified directory (ANALYSIS_HOME).