Argv split cmdline string as array of argument array by the '|' character.

NewParser create a cmdline string parser.

NewScanner create a scanner and init it's internal states.

Scan is a utility function help split input text as tokens.

TokBackQuote is reverse quoted string.

TokEOF means the input end.

TokPipe is the '|' character.

TokSpace represent space character sequence.

TokString for string.

ErrInvalidSyntax was reported if there is a syntax error in command line string.

Scanner is a cmdline string scanner.

Token is generated by the scanner with a type and value.

TokenType is the type of tokens recognized by the scanner.