#649 - syntax for calling external programs without capturing the output

CHANGELOG.md

@@ -25,6 +25,7 @@
   * Add `Transformed` pattern
   * Add experimental `Capture` pattern for capturing values
   * Add experimental `Branch` pattern for multiple matches
+* Add `$[...]` syntax for running external programs without capturing output
 
 ### Fixes and improvements
 * Fix `AtPath` for non-eachables

lib/stdlib.ngs

@@ -6806,6 +6806,14 @@ TEST "$(/bin/echo -n abc)" == 'abc'
 TEST $(cd:"/" pwd).lines()[0] == '/'
 TEST t=TmpFile(); $(echo -n abc >$t); t.read() == "abc"
 
+doc Same as $(top_level:: ...) - run the commands without capturing the stdout/stderr.
+doc Use the same stdout/stderr as the parent process (your script).
+F '$[]'(cp:CommandsPipeline) {
+	debug("process2", { "Using \$[] to set top_level:: for ${cp}" })
+	cp.options.top_level = true
+	$($cp)
+}
+
 doc Write to first process of ProcessesPipeline
 doc %EX - p = (|cat -n | tac >/tmp/1)
 doc %EX - p.write("one\n")

syntax.leg

@@ -1464,7 +1464,7 @@ identifier =
 		ret->name = ngs_strdup(yytext);
 		$$ = ret;
 	}
-	| "(" <("$()" | [-|=!@?~+*/%$<>.\[\]:]+ | "is not" | "not in")> ")" {
+	| "(" <("$()" | "$[]" | [-|=!@?~+*/%$<>.\[\]:]+ | "is not" | "not in")> ")" {
 		MAKE_NODE(ret, IDENTIFIER_NODE);
 		ret->name = ngs_strdup(yytext);
 		$$ = ret;
@@ -1721,6 +1721,7 @@ optional-function-call-arguments =
 
 subshell =
 	"$(" cmd:commands-pipeline ")" { $$ = cmd; }
+	| "$[" cmd:commands-pipeline "]" { $$ = cmd; cmd->first_child->name = ngs_strdup("$[]"); $$ = cmd; }
 	| "%(" cmd:commands-pipeline ")" { cmd->first_child->name = ngs_strdup("%()"); $$ = cmd; }
 	| "``" cmd:commands-pipeline "``" { cmd->first_child->name = ngs_strdup("````"); $$ = cmd; }
 	| "`" cmd:commands-pipeline "`" { cmd->first_child->name = ngs_strdup("``");  $$ = cmd; }