I'm trying to get the output of pdftk command with execSync. Here is the code:

const { execSync } = require('child_process');
const result = execSync(`pdftk ${fileName} dump_data_fields`);

After execution result contains an empty Buffer. At the same time if I set the output option to inherit {stdio: 'inherit'} the output of the command will be printed to console, so the command works fine. Here is a full code of such case:

const { execSync } = require('child_process');
execSync(`pdftk ${fileName} dump_data_fields`,{stdio: 'inherit'});

Also simple commands like echo Hello world works fine and it's output stored in result.

What I'm doing wrong with the pdftk command?