Differences

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--- playground:plan9_tutorial_sam [2021/04/19 21:31] – dsp
+++ playground:plan9_tutorial_sam [2021/04/20 04:59] (current) – adding external command section dsp
@@ Line 93: / Line 93: @@
 , x/{$/ -/^[ 	]*/ t .+0
 </code>
+=== Interacting with external commands ===
+Of course creating a indentation program with just regexp would be duplication of work.
+For most languages pretty printers exist like gofmt and cb (C beautifier) let' try
+to run cb on some ugly-fied C.
+<code>
+if  (foo <bar(bz)) {
+	  do(bxm,as);
+wrong;
+   }
+</code>
+To pass all this code through cb we can just select it and then
+issue the command |cb . that would replace the dot by
+<code>
+if  (foo <bar(bz)) {
+	do(bxm,as);
+	wrong;
+}
+</code>
+similarly we can read input from a command
+using < and write to a command using > if we want to count all the
+characters in a selection for example we can highlight it and issue >wc
+, observe that this doesn't changes our current text
+We could also imagine a command where it replaces every
+occurrence of //{DATE}// with the current system date in the whole document
+<code>
+, x/{DATE}/ <date
+</code>
+would find any occurrence of the string //{DATE}// and then replace that
+dot with the output of the date command.
 === Self guided discoveries ===