Re: [9fans] rc scripts, how to get spaces in array elements generated by command output?

[Mack Wallace <mackbw@mapinternet.com>]

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Thank you Anthony!

I had thought that IFS in Plan 9 was not the way to go after reading from ‘Rc - The Plan 9 Shell’ 

     “IFS is no longer used, except in the one case where it was indispensable:
      converting command output into argument lists during command substitution.”

The document then followed about avoiding a UNIX security hole, and lacking examples was not sure what this meant. Of course, in retrospect, it means exactly what I want to do.

So what I’ve ended up doing:

headrec = `{read $1 | sed ’s/^/,/; s/\\”/☹/g; s/,”([^”]*)”/,☺\1☻/g; s/,”/,☺/; :MC; s/☺([^☻]*),([^☻]*)/☺\1☯\2/g; tMC; s/^,//; s/,/♪/g’}
oldifs = $ifs
ifs = ♪
headers = `{echo $headrec | sed ‘/s/☹/\\”/g; s/(☺|☻)/“/g; s/☯/,/g’}
ifs = $oldifs

I’m not sure if there is a cleaner way to do this - but it gets the array of headers how they should be.

I’ll look at your other message.

Thanks,

Mack




> On Jan 5, 2019, at 6:52 PM, Anthony Martin <ality@pbrane.org> wrote:
> 
> Mack Wallace <mackbw@mapinternet.com> once said:
>> My question: Is there a way to take the string output of a command that
>> contains spaces and make it a single element of an array in rc script?
>> 
>> [...]
>> 
>> However, if I am receiving output from sed that contains spaces from
>> the following script line
>> 
>> string_var = `{echo some_string | sed ’s/x/y/g’}
>> 
>> If the output was ‘hello world’, string_var would become a two
>> element array which
>> echo $some_string(1) 
>> echo $some_string(2)
>> 
>> Would output 
>> hello
>> world
> 
> You need to change the input field separator, $ifs.
> 
> The default value is any whitespace character:
> 
> 	% x = `{echo -n hello world}
> 	% echo $#x
> 	2
> 	% echo $x(1)
> 	hello
> 	% echo $x(2)
> 	world
> 
> Using only newline as the separator yields:
> 
> 	% ifs = '
> 		' # this is a newline character
> 	% 	y = `{echo -n hello world}
> 	% echo $#y
> 	1
> 	% echo $y(1)
> 	hello world
> 
> You might want to use a comma instead:
> 
> 	% ifs = ,
> 	% z = `{echo -n hello world,good luck}
> 	% echo $#z
> 	2
> 	% echo $z(1)
> 	hello world
> 	% echo $z(2)
> 	good luck
> 
> Cheers,
>  Anthony
> 
> 


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