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1bf2b43d30
For compound commands we already have begin/end but
> it is long, which it is not convenient for the command line
> it is different than {} which shell users have been using for >50 years
The difference from {} can break muscle memory and add extra steps
when I'm trying to write simple commands that work in any shell.
Fix that by embracing the traditional style too.
---
Since { and } have always been special syntax in fish, we can also
allow
{ }
{ echo }
which I find intuitive even without having used a shell that supports
this (like zsh. The downside is that this doesn't work in some other
shells. The upside is in aesthetics and convenience (this is for
interactive use). Not completely sure about this.
---
This implementation adds a hack to the tokenizer: '{' is usually a
brace expansion. Make it compound command when in command position
(not something the tokenizer would normally know). We need to disable
this when parsing a freestanding argument lists (in "complete somecmd
-a "{true,false}"). It's not really clear what "read -t" should do.
For now, keep the existing behavior (don't parse compound statements).
Add another hack to increase backwards compatibility: parse something
like "{ foo }" as brace statement only if it has a space after
the opening brace. This style is less likely to be used for brace
expansion. Perhaps we can change this in future (I'll make a PR).
Use separate terminal token types for braces; we could make the
left brace an ordinary string token but since string tokens undergo
unescaping during expansion etc., every such place would need to know
whether it's dealing with a command or an argument. Certainly possible
but it seems simpler (especially for tab-completions) to strip braces
in the parser. We could change this.
---
In future we could allow the following alternative syntax (which is
invalid today).
if true {
}
if true; {
}
Closes #10895
Closes #10898
59 lines
1.5 KiB
ReStructuredText
59 lines
1.5 KiB
ReStructuredText
.. _cmd-begin:
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begin - start a new block of code
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=================================
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Synopsis
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--------
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.. synopsis::
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begin; [COMMANDS ...]; end
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{ [COMMANDS ...] }
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Description
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-----------
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``begin`` is used to create a new block of code.
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A block allows the introduction of a new :ref:`variable scope <variables-scope>`, redirection of the input or output of a set of commands as a group, or to specify precedence when using the conditional commands like ``and``.
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The block is unconditionally executed. ``begin; ...; end`` is equivalent to ``if true; ...; end``.
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``begin`` does not change the current exit status itself. After the block has completed, ``$status`` will be set to the status returned by the most recent command.
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Some other shells only support the ``{ [COMMANDS ...] ; }`` notation.
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The **-h** or **--help** option displays help about using this command.
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Example
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-------
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The following code sets a number of variables inside of a block scope. Since the variables are set inside the block and have local scope, they will be automatically deleted when the block ends.
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::
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begin
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set -l PIRATE Yarrr
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...
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end
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echo $PIRATE
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# This will not output anything, since the PIRATE variable
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# went out of scope at the end of the block
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In the following code, all output is redirected to the file out.html.
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::
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begin
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echo $xml_header
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echo $html_header
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if test -e $file
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...
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end
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...
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end > out.html
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