How to set a search_path default on a psql cmd execution?

I finally found it, its not a psql option, but it fits a oneliner: PGOPTIONS=--search_path=myschema psql -h myHost -U myUser -dmyDb -p myPort.

If anybody improves it with a working version call for both unix and windows ill approve

You could use the .psqlrc file, which is run at psql startup:

$ echo 'set search_path to foo,bar' >> ~/.psqlrc
$ psql ...

You can specify a PGOPTIONS-style connstring as an argument to psql instead of using the -d/-h/-U/-p/etc options. For your example:

psql 'host=myHost user=myUser dbname=myDb port=myPort options=--search_path=myschema'

or, if you prefer the URI style,

psql 'postgresql://myUser@myHost:myPort/myDb?options=--search_path%3dmyschema'

See the "Connection strings" section of the manual for details.