How to check varnish syntax ?

Restarting varnish server for checking syntax and applying the modification could get so wrong beacaues incorrect syntax might lead to abort varnish server and your site would go down.

To check varnish configuration:

varnishd -C -f /etc/varnish/default.vcl

If syntax is correct, varnish will then dump out the generated configuration.

Otherwise you’ll get an error message pointing you to a specific line number and error position.