Removing an element from an array

Removing an element from an array

[Peter Slížik]

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Hello,

I would like to remove an element from an array - actually a path from the
$path variable. After some googling, I've discovered the ${array:|excl}
syntax.

Here is my code:

excl=($path_to_remove)
echo "path type: ${(t)path}
# -> path type: array-tied-export-special

export path=${path:|excl}
# -> export:19: path: inconsistent type for assignment

What am I doing wrong? Actually, as the command ends up with an exception,
I'm not able to verify whether 'path' is an array or a scalar after the
command.

This is the relevant part of the documentation. I don't think any of the
conditions in the second sentence is relevant to the error message.

${name:|arrayname}

If arrayname is the name (N.B., not contents) of an array variable, then
any elements contained in arrayname are removed from the substitution of
name. If the substitution is scalar, either because name is a scalar
variable or the expression is quoted, the elements of arrayname are instead
tested against the entire expression
Any suggestions?
Peter

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Re: Removing an element from an array

[Roman Perepelitsa]

On Mon, Nov 2, 2020 at 12:11 PM Peter Slížik <peter.slizik@gmail.com> wrote:
>
> I would like to remove an element from an array - actually a path from the $path variable. After some googling, I've discovered the ${array:|excl} syntax.
>
> Here is my code:
>
> excl=($path_to_remove)
> export path=${path:|excl}

This is pretty close. Here's the correct syntax:

    excl=($path_to_remove)
    path=(${path:|excl})

However, if you want to remove just one element, there is a simpler way:

    path=(${path:#$path_to_remove})

Roman.

Re: Removing an element from an array

[Peter Slížik]

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Dear Roman,

thank you for both suggestions.

By the way,  can I ask why it is necessary to re-introduce the array
context by another pair of parentheses, if the expression already produces
an array value?

Or does the ${...:|...} expression produce a string which needs to be
parsed again? Would this cause problems if any of the path elements
contained a space in the file name?

Thank you,
Peter

пон, 2. нов 2020. у 12:25 Roman Perepelitsa <roman.perepelitsa@gmail.com>
је написао/ла:

> On Mon, Nov 2, 2020 at 12:11 PM Peter Slížik <peter.slizik@gmail.com>
> wrote:
> >
> > I would like to remove an element from an array - actually a path from
> the $path variable. After some googling, I've discovered the ${array:|excl}
> syntax.
> >
> > Here is my code:
> >
> > excl=($path_to_remove)
> > export path=${path:|excl}
>
> This is pretty close. Here's the correct syntax:
>
>     excl=($path_to_remove)
>     path=(${path:|excl})
>
> However, if you want to remove just one element, there is a simpler way:
>
>     path=(${path:#$path_to_remove})
>
> Roman.
>

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Re: Removing an element from an array

[Bart Schaefer]

On Mon, Nov 2, 2020 at 4:23 AM Peter Slížik <peter.slizik@gmail.com> wrote:
>
> By the way,  can I ask why it is necessary to re-introduce the array context by another pair of parentheses, if the expression already produces an array value?

Assignment without the parens is a scalar context; the existing type
of the variable named on the left side is not considered during
parsing, and if the variable is not "special" the type may actually be
changed from array to scalar by the assignment operation.