Execline: Difference between revisions

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== 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 ==

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</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.

{ pkgs ? import <nixpkgs> { } }:

pkgs.execline.passthru.writeScript "wrap-cowsay" "-s0" ''

pipeline -w { ${pkgs.lib.getExe pkgs.cowsay} "-r" }

$@

''

</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

builtins.foldl' (acc: arg: acc ++ (

if builtins.isList arg

then map (_: " ${_}") (quoteExecline arg) ++ [ "" ]

else [ arg ]

)) [ ];

</syntaxHighlight>

then the expression

args: lib.escapeShellArgs (quoteExecline [ "pipeline" "-w" [ (lib.getExe pkgs.cowsay) "-r" ] ] ++ args)

</syntaxHighlight>

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]]

@@ Line 3: / Line 3: @@
 == 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 ==
@@ Line 44: / Line 44: @@
 </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} "-r" }
+  $@
+''
+</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) "-r" ] ] ++ args)
+</syntaxHighlight>
+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]]