Re: [9fans] silly rc quoting question

Re: [9fans] silly rc quoting question

[erik quanstrom]

how about
	; eval 'a = (' `{cat junk} ')'
	; whatis a
	a=(f1 f2 'free text' f4)
	; echo $#a
	4

the reason that your original failed is that /bin/read returns one
line at a time.  the rc backquote operator then tokenizes not
according to rc's syntax rules but by $ifs.  the default for $ifs is
space, newline, tab.  thus the string
	f1 f2 'free text' f4newline
is parsed as
	"f1", "f2", "'free", "text'", f4

- erik

On Mon Dec 18 06:34:41 EST 2006, steve@quintile.net wrote:
> I have realised I don't understand rc's quoting
> rules as well as I thought I did. I want to parse
> the output of a program which has one record per line,
> and white space delimited fields in each line.
> 
> Some fields have whitespace in them but if they do then
> these fields are surrounded in quotes; here I will use cat
> and a file as an example, in "real life" its all a
> bit more complex.
> 
> 	term% cat junk
> 	f1 f2 'free text' f4
> 
> I expect when I parse this using the backquote operator then
> the quoting would be respected, this appears not to be
> the case:
> 
> 	term% cat junk | while(a=`{read}){
> 		echo $#a
> 		echo $a(3)
> 	}
> 	5
> 	'free
> 
> Where as I would expect:
> 
> 	4
> 	free text
> 
> I know I cannot do this with awk (unless I build the parser in awk
> (ugh)). Having said this I have been tempted to produce a non-standard,
> awk9 which understands plan9's unified quoting rules, even things like
> 
> 	ls -l | awk '{print $6, $10}'
> 
> are not reliable given whitespace in file names.
> 
> Is it possible to use rc to parse data using rc's rules?
> 
> -Steve

Re: [9fans] silly rc quoting question

[Russ Cox]

If you know that the output file is correctly quoted,
like the output of ls, then you can turn it into a shell
script and then pass it to rc.

For example:

  fn x {
    echo $1
  }
  . <{ls | sed 's/^/x /'}

Russ

Re: [9fans] silly rc quoting question

[erik quanstrom]

Well, Don't Do That, Then. ☺

this awk script will do what you want
	ls -l|awk '{print substr($0, 38+length($4)+length($5));}'

it's slightly annoying, but unavoidable that ls -l's user and group
fields are dynamicly sized.

- erik

[9fans] silly rc quoting question

[Steve Simon]

I have realised I don't understand rc's quoting
rules as well as I thought I did. I want to parse
the output of a program which has one record per line,
and white space delimited fields in each line.

Some fields have whitespace in them but if they do then
these fields are surrounded in quotes; here I will use cat
and a file as an example, in "real life" its all a
bit more complex.

	term% cat junk
	f1 f2 'free text' f4

I expect when I parse this using the backquote operator then
the quoting would be respected, this appears not to be
the case:

	term% cat junk | while(a=`{read}){
		echo $#a
		echo $a(3)
	}
	5
	'free

Where as I would expect:

	4
	free text

I know I cannot do this with awk (unless I build the parser in awk
(ugh)). Having said this I have been tempted to produce a non-standard,
awk9 which understands plan9's unified quoting rules, even things like

	ls -l | awk '{print $6, $10}'

are not reliable given whitespace in file names.

Is it possible to use rc to parse data using rc's rules?

-Steve