Fwd: more splitting travails

[Bart Schaefer <schaefer@brasslantern.com>]

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This was sent privately to me but pretty obviously intended for the list.

---------- Forwarded message ---------
From: Mark J. Reed <markjreed@gmail.com>
Date: Fri, Jan 12, 2024, 11:54 AM
Subject: Re: more splitting travails
To: Bart Schaefer <schaefer@brasslantern.com>


We talked offlist about how zsh inherited the paradoxical-looking and
"${array[@]}" from earlier shells,  though it works differently such that a
simple $array usually does what you want?

Well, here's where the exception to that "usually" comes in.

Although the elements of an array expanded as simply $array don't get
generally re-split on whitespace the way an unquoted ${array[@]} or
${array[*]} does in bash, any elements that are completely empty do get
lost:

        *zsh% *array=(one two '' '' five )
    *zsh% *echo $#array
    5
    *zsh%* printf '%s\n' $array # King Arthur, is that you?
    one
    two
    five
    *zsh% *

So that's where you need the wonky inherited syntax if you want to include
empty values:

    *zsh%* printf '%s\n' "${array[@]}"
    one
    two


    five
    *zsh%*

Bart's question is also salient, however:

    > I have a file with blank lines in it, I read it into a variable

How do you read it in, and into what kind of variable? If you want to read
a file into an array of lines, preserving empty lines, you can do this:

    lines=("${(@f)$(<~"$filename")}")

 The stuff in parentheses just inside the ${ are parameter expansion flags,
which you can read about on the zshexpn man page.  In particular, the f
flag splits the value on newlines, while the @ flag does the same thing as
"${array[@]}" (which could therefore also be written as "${(@)array}"), but
also works in other kinds of expansions, such as $(<filename) used here
(which means  "get the contents of the file").

On Fri, Jan 12, 2024 at 2:19 PM Bart Schaefer <schaefer@brasslantern.com>
wrote:

> On Fri, Jan 12, 2024 at 11:05 AM Ray Andrews <rayandrews@eastlink.ca>
> wrote:
> >
> > There's nothing harder than really getting on top of splitting issues :(
> >
> > I have a file with blank lines in it, I read it into a variable
>
> This is probably the place you're getting messed up.  HOW do you read
> it into a variable?
>
> > Other various attempts give me the number of elements being the
> > character count.  Weirdly there's places where I iterate over all the
> > lines in 'List' and it *counts* nine, but only displays five.
>
> Here you've probably done an earlier step right, but are forgetting to
> quote what you're passing to print (or whatever "display" means).  The
> default for arrays on the command line is to remove empty elements
> unless quoted.
>
>

-- 
Mark J. Reed <markjreed@gmail.com>

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