How to run NPM Command in Java code using ProcessBuilder

Question

My environment is mac. I'm trying to run "npm ls" from my java code but it throws error messages.

My java code:

String npm = isWindows() ? "npm.cmd" : "npm";

System.out.println(rootStr);
Process process = new ProcessBuilder(npm, "ls").directory(new File(rootStr)).start();

Error Message:

Users/youngeun/Downloads/zenbot_unstable
java.io.IOException: Cannot run program "npm" (in directory "/Users/youngeun/Downloads/zenbot_unstable"): error=2, No such file or directory
    at java.lang.ProcessBuilder.start(ProcessBuilder.java:1048)
    at com.iotcube.scanner.nodejs.npm.NpmService.npmInfo(NpmService.java:26)
    at com.iotcube.scanner.IotcubescannerApplication.main(IotcubescannerApplication.java:174)
Caused by: java.io.IOException: error=2, No such file or directory
    at java.lang.UNIXProcess.forkAndExec(Native Method)
    at java.lang.UNIXProcess.<init>(UNIXProcess.java:247)
    at java.lang.ProcessImpl.start(ProcessImpl.java:134)
    at java.lang.ProcessBuilder.start(ProcessBuilder.java:1029)
    ... 2 more

But it seems to work perfectly in my terminal:

| ~/Downloads/zenbot_unstable @ Youngeunui-MacBook-Pro (youngeun) 
| => npm ls
[email protected] /Users/youngeun/Downloads/zenbot_unstable
├─┬ @babel/[email protected]
│ ├─┬ @babel/[email protected]
│ │ └─┬ @babel/[email protected]
│ │   ├── [email protected] deduped
│ │   ├── [email protected] deduped
│ │   └── [email protected]
│ ├─┬ @babel/[email protected]
│ │ ├── @babel/[email protected] deduped
│ │ ├── [email protected]
│ │ ├── [email protected] deduped
...

I've tried solutions from other stackoverflow pages but none of them seems to work... I am so lost.. I would appreciate your help. thanks

Answer 1

Try providing full path to the npm executable:

String dir = "/Users/youngeun/Downloads/zenbot_unstable";
String npm = dir + "/npm";
Process p = new ProcessBuilder(npm, "ls")
                .director(new File(dir))
                .start();
p.waitFor();