# HG changeset patch
# User František Kučera <franta-hg@frantovo.cz>
# Date 1557052663 -7200
# Node ID 86de8e6ab231971b8dad9e85ea771563a6b722bb
# Parent  050ec7c1f2e7e839aaf8becdd9383c19238b81da
documentation

diff -r 050ec7c1f2e7 -r 86de8e6ab231 src/AwkHandler.h
--- a/src/AwkHandler.h	Sun May 05 11:54:53 2019 +0200
+++ b/src/AwkHandler.h	Sun May 05 12:37:43 2019 +0200
@@ -50,6 +50,14 @@
 using namespace relpipe::reader;
 using namespace relpipe::reader::handlers;
 
+/**
+ * This transformation consists of three processes connected together using pipes.
+ * 
+ * Processes:
+ *	- Parent: process RelationalReaderStringHandler events (read relational data, usually from STDIN) and pass them in the special text format to the pipe1
+ *  - AWK: external program (/usr/bin/awk), read from the pipe1, writes to the pipe2
+ *  - Writer: reads from the pipe2 and writes to relationalWriter (relational data, usually to STDOUT)
+ */
 class AwkHandler : public RelationalReaderStringHandler {
 private:
 	Configuration configuration;
@@ -78,6 +86,7 @@
 	void cleanUp() {
 		if (awkInputWriterFD >= 0) {
 			closeOrThrow(awkInputWriterFD);
+			// TODO: check exit codes
 			__pid_t waitResult1 = wait(NULL);
 			__pid_t waitResult2 = wait(NULL);
 			awkInputWriterFD = -1;
@@ -112,9 +121,8 @@
 			redirectFD(awkInputReaderFD, STDIN_FILENO);
 			redirectFD(awkOutputWriterFD, STDOUT_FILENO);
 
-
+			// Runs AWK program found on $PATH → user can plug-in a custom implementation or a wrapper, but this can be also bit dangerous (however AWK itself is dangerous).
 			execlp("awk", "awk", "{print \"AWK says: line \" NR \" = \" $0;}", nullptr);
-
 		} else {
 			// Parent process
 			closeOrThrow(awkInputReaderFD);