How do field delimiters work in pg_dump?

I have a file containing the contents of a postgresql schema. The file was created with pg_dump, without specifying any optional field separator parameters. I need to read the file in line-by-line with a script, do some checks on fields, then output to another file.

Through experimentation I have verified that both spaces and tabs do not seem to be the delimiters between fields in the dump file. Further, the fields contain a lot of 'random' content, and could include spaces and tabs themselves.

So, how do field delimiters work in pg_dump?