pipeline How to do I get the output of a shell command executed using into a variable from Jenkinsfile (groovy)?

参考:
https://stackoverflow.com/questions/36547680/how-to-do-i-get-the-output-of-a-shell-command-executed-using-into-a-variable-fro
https://jenkins.io/doc/pipeline/steps/workflow-durable-task-step/#code-sh-code-shell-script


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def check_packet_num = sh(returnStdout: true, script: "echo ${ue_path}/log")  //script 使用‘’不支持外部变量，使用""支持外部变量