pgrep -P, but for grandchildren not just children

Question

I am using:

pgrep -P $$

to get the child pids of $$. But I actually want a list of grandchildren and great grandchild too.

How do I do this tho? With a regular programming language we would do that with recursion for example, but with bash? Perhaps use a bash function?

Answer 1

I ended up doing this with node.js and bash:

 const async = require('async');
 const cp = require('child_process');

 export const getChildPids = (pid: number, cb: EVCb<Array<string>>) => {

      const pidList: Array<string> = [];

      const getMoreData = (pid: string, cb: EVCb<null>) => {

        const k = cp.spawn('bash');
        const cmd = `pgrep -P ${pid}`;
        k.stderr.pipe(process.stderr);
        k.stdin.end(cmd);
        let stdout = '';
        k.stdout.on('data', d => {
          stdout += String(d || '').trim();
        });

        k.once('exit', code => {

          if (code > 0) {
            log.warning('The following command exited with non-zero code:', code, cmd);
          }

          const list = String(stdout).split(/\s+/).map(v => String(v || '').trim()).filter(Boolean);

          if (list.length < 1) {
            return cb(null);
          }

          for (let v of list) {
            pidList.push(v);
          }

          async.eachLimit(list, 3, getMoreData, cb);

        });
      };

      getMoreData(String(pid), err => {
        cb(err, pidList);
      });

    };