Execline - Revision history

Ehmry: add "See also" section

2025-07-19T12:52:25Z

add "See also" section

← Older revision		Revision as of 12:52, 19 July 2025
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	</syntaxHighlight>		</syntaxHighlight>
	would produce the command-line executed by <code>execlineb</code> in the previous "wrap-cowsay" example when given the same arguments.		would produce the command-line executed by <code>execlineb</code> in the previous "wrap-cowsay" example when given the same arguments.

			== See also ==

			execline scripts can be found in the following repositories:
			* [https://spectrum-os.org/git/spectrum/ Spectrum]
			* [https://github.com/search?q=repo%3Aaanderse%2Ffinix%20execline&type=code Finix]

	[[Category:Cookbook]]		[[Category:Cookbook]]

Ehmry: fix typo

2025-07-19T12:43:10Z

fix typo

← Older revision		Revision as of 12:43, 19 July 2025
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	== execlineb ==		== execlineb ==

	[https://skarnet.org/software/execline/execlineb.html execlineb] is the interpreter for execline scripts. It reads a file, produces a command-line, and executes into that command line. <code>execlineb</code> manages the environment of the command that it executes and ~~optionaly~~ substitutes the arguments a script receives into the command-line. <code>execlineb</code> also handles the quoting of strings using <code>""</code> and blocks using <code>{}</code>. Blocks are described later in this article.		[https://skarnet.org/software/execline/execlineb.html execlineb] is the interpreter for execline scripts. It reads a file, produces a command-line, and executes into that command line. <code>execlineb</code> manages the environment of the command that it executes and optionally substitutes the arguments a script receives into the command-line. <code>execlineb</code> also handles the quoting of strings using <code>""</code> and blocks using <code>{}</code>. Blocks are described later in this article.

	== Wrappers ==		== Wrappers ==

Ehmry: blocks: add an argument to cowsay

2025-07-19T12:37:31Z

blocks: add an argument to cowsay

← Older revision		Revision as of 12:37, 19 July 2025
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	pkgs.execline.passthru.writeScript "wrap-cowsay" "-s0" ''		pkgs.execline.passthru.writeScript "wrap-cowsay" "-s0" ''
	pipeline -w { ${pkgs.lib.getExe pkgs.cowsay} }		pipeline -w { ${pkgs.lib.getExe pkgs.cowsay} "-r" }
	$@		$@
	''		''
Line 71:		Line 71:
	then the expression		then the expression
	<syntaxHighlight lang="nix">		<syntaxHighlight lang="nix">
	args: lib.escapeShellArgs (quoteExecline [ "pipeline" "-w" [ (lib.getExe pkgs.cowsay) ] ] ++ args)		args: lib.escapeShellArgs (quoteExecline [ "pipeline" "-w" [ (lib.getExe pkgs.cowsay) "-r" ] ] ++ args)
	</syntaxHighlight>		</syntaxHighlight>
	would produce the command-line executed by <code>execlineb</code> in the previous "wrap-cowsay" example when given the same arguments.		would produce the command-line executed by <code>execlineb</code> in the previous "wrap-cowsay" example when given the same arguments.

	[[Category:Cookbook]]		[[Category:Cookbook]]

Ehmry: blocks section

2025-07-19T12:34:18Z

blocks section

← Older revision		Revision as of 12:34, 19 July 2025
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	</syntaxHighlight>		</syntaxHighlight>

			== Blocks ==

			Some execline programs take code blocks as their arguments. Blocks are delimited by <code>{}</code> in execlineb scripts. In the following example the <code>pipeline</code> program executes a block of commands in the background with a pipe connecting the stdin of that block to the stdout of the command-line following the block.

			<syntaxHighlight lang="nix">
			{ pkgs ? import <nixpkgs> { } }:

			pkgs.execline.passthru.writeScript "wrap-cowsay" "-s0" ''
			pipeline -w { ${pkgs.lib.getExe pkgs.cowsay} }
			$@
			''
			</syntaxHighlight>

			=== Block quoting ===

			execlineb parses <code>{}</code> blocks and constructs a command-line where each block item is prepended with a whitespace (\x20) and terminated with an empty string. This quoting can be done in pure Nix.

			Given the function <code>quoteExecline</code> as
			<syntaxHighlight lang="nix">
			builtins.foldl' (acc: arg: acc ++ (
			if builtins.isList arg
			then map (_: " ${_}") (quoteExecline arg) ++ [ "" ]
			else [ arg ]
			)) [ ];
			</syntaxHighlight>
			then the expression
			<syntaxHighlight lang="nix">
			args: lib.escapeShellArgs (quoteExecline [ "pipeline" "-w" [ (lib.getExe pkgs.cowsay) ] ] ++ args)
			</syntaxHighlight>
			would produce the command-line executed by <code>execlineb</code> in the previous "wrap-cowsay" example when given the same arguments.

	[[Category:Cookbook]]		[[Category:Cookbook]]

Ehmry: initial article with wrappers sections

2025-07-19T12:04:24Z

initial article with wrappers sections

New page

[https://skarnet.org/software/execline/index.html execline] is an interpreter and a collection of utilities for composing Unix commands into scripts. The syntax of execline makes it better suited for code generation from Nix than interactive shell languages like [[Bash]].

== execlineb ==

[https://skarnet.org/software/execline/execlineb.html execlineb] is the interpreter for execline scripts. It reads a file, produces a command-line, and executes into that command line. <code>execlineb</code> manages the environment of the command that it executes and optionaly substitutes the arguments a script receives into the command-line. <code>execlineb</code> also handles the quoting of strings using <code>""</code> and blocks using <code>{}</code>. Blocks are described later in this article.

== Wrappers ==

Consider the scenario of wrapping a program to override or set a default value for the <code>EDITOR</code> enviroment variable.

The following example is a script that uses the [https://skarnet.org/software/execline/export.html export] program to set <code>EDITOR</code>. Here the <code>-s0</code> option is used to replace <code>$1</code> and <code>$@</code> within the command-line with the first and remaining arguments received by the script.

{{file|wrap-editor.el||
<nowiki>
#! /usr/bin/env execlineb -s1
export EDITOR $1
$@
</nowiki>}}

If the script is executed as <code>wrap-editor.el nano mutt</code> then the command-line executed by execlineb would be <code> export nano mutt</code>.

To create a wrapper that would provide a default <code>EDITOR</code> the [https://skarnet.org/software/execline/importas.html importas] program would be used. In the following example the <code>EDITOR</code> value is imported from the calling enviroment, with a default value specified by <code>-D</code>, and any instance of <code>$editor</code> is replaced by that value. The <code>export</code> program exports the value of <code>$editor</code> after substitution.

{{file|wrap-default-editor.el||
<nowiki>
#! /usr/bin/env execlineb -s1
importas -D $1 EDITOR $editor
export EDITOR $editor
$@
</nowiki>}}

=== Generating a wapper from Nix ===

To generate a wrapper with a fixed default for <code>EDITOR</code> the Nix function at <code>execline.passthru.writeScript</code> can be used:

<syntaxHighlight lang="nix">
{ pkgs ? import <nixpkgs> { } }:

pkgs.execline.passthru.writeScript "wrap-nano" "-s0" ''
importas -D ${pkgs.nano}/bin/nano EDITOR E
export EDITOR $E
$@
''
</syntaxHighlight>

[[Category:Cookbook]]