diff --git a/Makefile b/Makefile
index 44047c50..1467310e 100644
--- a/Makefile
+++ b/Makefile
@@ -48,7 +48,7 @@ log/jshint.log: log/npm-dev-install.log lib/spellcast.js test/spellcast-test.js
 
 # Mocha BDD STDOUT test
 log/mocha.log: log/npm-dev-install.log lib/spellcast.js test/spellcast-test.js
-	${MOCHA} test/spellcast-test.js -R list | tee log/mocha.log ; exit $${PIPESTATUS[0]}
+	${MOCHA} test/spellcast-test.js -R spec | tee log/mocha.log ; exit $${PIPESTATUS[0]}
 
 # README
 README.md: documentation.md bdd-spec.md
diff --git a/README.md b/README.md
index 8aa7c56f..343f5f70 100644
--- a/README.md
+++ b/README.md
@@ -19,6 +19,12 @@ Full BDD spec generated by Mocha:
 echo
 delayed-echo
 bob blihblih one
+scroll line: one
+scroll line: three
+scroll line: two
+scroll line: one
+scroll line: three
+scroll line: two
 one more time: one
 one more time: two
 one more time: three
@@ -74,7 +80,7 @@ cleanup( function() {
 } ) ;
 ```
 
-should substitute variable (aka formula) accordingly.
+should substitute variable (aka formula) accordingly in 'sh' block.
 
 ```js
 cleanup( function() {
@@ -90,6 +96,22 @@ cleanup( function() {
 } ) ;
 ```
 
+should write a new formula with the output of an 'sh' block.
+
+```js
+cleanup( function() {
+	
+	var book = new spellcast.Book( fs.readFileSync( 'spellbook' ).toString() ) ;
+	
+	book.cast( 'write-formula' , function( error )
+	{
+		expect( error ).not.ok() ;
+		expect( getCastedLog( 'write-formula' ) ).to.be( 'scroll line: one\nscroll line: three\nscroll line: two\nscroll line: one\nscroll line: three\nscroll line: two\n' ) ;
+		done() ;
+	} ) ;
+} ) ;
+```
+
 <a name="foreach-block"></a>
 # 'foreach' block
 should .
diff --git a/bdd-spec.md b/bdd-spec.md
index 8354713e..d6d34ba2 100644
--- a/bdd-spec.md
+++ b/bdd-spec.md
@@ -1,6 +1,12 @@
 echo
 delayed-echo
 bob blihblih one
+scroll line: one
+scroll line: three
+scroll line: two
+scroll line: one
+scroll line: three
+scroll line: two
 one more time: one
 one more time: two
 one more time: three
@@ -56,7 +62,7 @@ cleanup( function() {
 } ) ;
 ```
 
-should substitute variable (aka formula) accordingly.
+should substitute variable (aka formula) accordingly in 'sh' block.
 
 ```js
 cleanup( function() {
@@ -72,6 +78,22 @@ cleanup( function() {
 } ) ;
 ```
 
+should write a new formula with the output of an 'sh' block.
+
+```js
+cleanup( function() {
+	
+	var book = new spellcast.Book( fs.readFileSync( 'spellbook' ).toString() ) ;
+	
+	book.cast( 'write-formula' , function( error )
+	{
+		expect( error ).not.ok() ;
+		expect( getCastedLog( 'write-formula' ) ).to.be( 'scroll line: one\nscroll line: three\nscroll line: two\nscroll line: one\nscroll line: three\nscroll line: two\n' ) ;
+		done() ;
+	} ) ;
+} ) ;
+```
+
 <a name="foreach-block"></a>
 # 'foreach' block
 should .
diff --git a/format.md b/format.md
index 3ac1620e..adc510bf 100644
--- a/format.md
+++ b/format.md
@@ -5,15 +5,17 @@
 
 # Variable substitution
 
-Variables aka formula are defined in the 'formula' block.
+Variables aka *formula* are defined in the *formula* block.
 
-A formula only consists of a string, no other type are supported ATM.
+A *formula* only consists of a string, no other type are supported ATM.
 
 Once a formula is defined, it can be used with the syntax `${variableName}`, where 'variableName' is the name
 of the variable.
 
 When a variable is encountered, it is substituted by its string value.
 
+TODOC: list formula
+
 
 
 # References
@@ -36,8 +38,19 @@ This block defines formula, i.e. variables and values used for substitution.
 * parallel: this shell block will execute each command in parallel mode, if a number is passed, this is the maximum
   of commands running in parallel
 * ignore: if a command return a non-zero status, it will continue nontheless
+* write-formula: this specify a variable name (aka a *formula*) which will be populated by each line of the output
+  of this shell block, the formula is used as a list
+* splitter: this specify a splitter for the 'write' argument, by default '\n' is the splitter
+* silence: dispell all output to stdout
+* amnesia: dispell all output to log files
 
 Each child of this block is a shell command to execute.
 
 
 
+## foreach <formula>
+
+TODOC: everything about foreach
+
+
+
diff --git a/lib/spellcast.js b/lib/spellcast.js
index ecb6d2bd..2b3b4f46 100644
--- a/lib/spellcast.js
+++ b/lib/spellcast.js
@@ -26,6 +26,7 @@
 
 /*
 	TODO:
+		* turn arguments using hyphen in spellbooks into camelCase (e.g. write-formula should be writeFormula in code)
 		* automatically check versus the 'spellbook' file (just like if 'spellbook' was added to all 'summon' block)
 		* escape formula variable substitution
 		* new blocks:
@@ -33,6 +34,7 @@
 			- wand
 			- zap
 			- ssh : like sh but remotely
+		* find the right regexp for split(/,/) because '\,' should not split
 */
 
 
@@ -661,31 +663,50 @@ spellcast.Book.prototype.castSummon = function castSummon( summon , castExecutio
 
 spellcast.Book.prototype.castShell = function castShell( shell , castExecution , callback )
 {
-	var plan ;
+	var plan , splitter , self = this ;
 	
 	plan = async
-		.foreach( shell.shellCommands , this.execShellCommand.bind( this , castExecution ) )
+		.map( shell.shellCommands , this.execShellCommand.bind( this , castExecution , shell.args ) )
 		.nice( 0 ) ;
 	
 	//console.log( shell ) ;
 	
-	if ( shell.args.parallel )
-	{
-		if ( shell.args.parallel === true ) { plan.parallel( shell.args.parallel ) ; }
-		else { plan.parallel( parseInt( shell.args.parallel ) ) ; }
-	}
+	if ( ! shell.args.parallel ) { plan.parallel( false ) ; }
+	else if ( shell.args.parallel === true ) { plan.parallel() ; }
+	else { plan.parallel( parseInt( shell.args.parallel ) ) ; }
 	
 	if ( ! shell.args.ignore ) { plan.fatal( true ) ; }
 	
-	plan.exec( callback ) ;
+	if ( shell.args['write-formula'] && typeof shell.args['write-formula'] !== 'string' ) { delete shell.args['write-formula'] ; }
+	
+	
+	// Let's exec the plan and process the final outcome!
+	
+	plan.exec( function( error , outputMap ) {
+		
+		if ( error ) { callback( error ) ; return ; }
+		
+		if ( shell.args['write-formula'] )
+		{
+			splitter = shell.args.splitter || '\n' ;
+			self.formula[ shell.args['write-formula'] ] = outputMap.join( '' ).trim().split( splitter ) ;
+			
+			/*
+			console.log( "outputMap:" , outputMap[0] ) ;
+			console.log( "full output:" , output ) ;
+			*/
+		}
+		
+		callback() ;
+	} ) ;
 	//plan.exec( function() { console.log( 'castShell: Done!' ) ; callback() ; } ) ;
 } ;
 
 
 
-spellcast.Book.prototype.execShellCommand = function execShellCommand( castExecution , shellCommand , callback )
+spellcast.Book.prototype.execShellCommand = function execShellCommand( castExecution , args , shellCommand , callback )
 {
-	var child , onStdout , onStderr , onStdin , onceExit , onIgnoredError ;
+	var child , onStdout , onStderr , onStdin , onceExit , onIgnoredError , output = '' ;
 	
 	//console.log( 'Exec command: ' , shellCommand ) ;
 	
@@ -705,41 +726,36 @@ spellcast.Book.prototype.execShellCommand = function execShellCommand( castExecu
 		
 		// For some reason, 'exit' can be triggered before some 'data' event, so we have to delay removeListener() a bit
 		setTimeout( function() {
+			
 			child.stdout.removeListener( 'data' , onStdout ) ;
 			child.stderr.removeListener( 'data' , onStderr ) ;
-		} , 200 ) ;
+			
+			// If there is an 'write-formula' arguments, we must trigger the callback in this timeout event,
+			// if not we take the risk that we will miss some output and we don't want that
+			if ( args['write-formula'] ) { callback( status , output ) ; }
+			
+		} , 0 ) ;
 		
-		callback( status ) ;
+		// If there isn't an 'write-formula' arguments, then we can trigger the callback now
+		if ( ! args['write-formula'] ) { callback( status ) ; }
 	} ;
 	
 	onStdout = function( chunk ) {
 		// Send the command's stdout to the process stdout and the output file
-		process.stdout.write( chunk ) ;
-		//castExecution.outputFile.write( 'Stdout:\n' ) ;
-		castExecution.outputFile.write( chunk ) ;
-		//castExecution.outputFile.write( '\n' ) ;
+		if ( ! args.silence ) { process.stdout.write( chunk ) ; }
+		if ( ! args.amnesia ) { castExecution.outputFile.write( chunk ) ; }
+		if ( args['write-formula'] ) { output += chunk ; }
 	} ;
 	
 	onStderr = function( chunk ) {
 		// Send the command's stderr to the process stderr and the output file
-		process.stderr.write( chunk ) ;
-		
-		//castExecution.outputFile.write( 'Stderr:\n' ) ;
-		castExecution.outputFile.write( chunk ) ;
-		//castExecution.outputFile.write( '\n' ) ;
+		if ( ! args.silence ) { process.stderr.write( chunk ) ; }
+		if ( ! args.amnesia ) { castExecution.outputFile.write( chunk ) ; }
 	} ;
 	
 	onStdin = function( chunk ) {
 		// Send the process stdin to the command's stdin
 		child.stdin.write( chunk ) ;
-		
-		// tmp:
-		/*
-		console.log( 'Received STDIN:' , chunk.toString() ) ;
-		castExecution.outputFile.write( 'Stdin:\n' ) ;
-		castExecution.outputFile.write( chunk ) ;
-		castExecution.outputFile.write( '\n' ) ;
-		*/
 	} ;
 	
 	// Prevent message sent to command that ignore them, then emit ECONNRESET when finished
diff --git a/test/ls/one b/test/ls/one
new file mode 100644
index 00000000..43dd47ea
--- /dev/null
+++ b/test/ls/one
@@ -0,0 +1 @@
+one
\ No newline at end of file
diff --git a/test/ls/three b/test/ls/three
new file mode 100644
index 00000000..1d19714f
--- /dev/null
+++ b/test/ls/three
@@ -0,0 +1 @@
+three
\ No newline at end of file
diff --git a/test/ls/two b/test/ls/two
new file mode 100644
index 00000000..64c5e588
--- /dev/null
+++ b/test/ls/two
@@ -0,0 +1 @@
+two
\ No newline at end of file
diff --git a/test/spellbook b/test/spellbook
index 60566803..5e97a328 100644
--- a/test/spellbook
+++ b/test/spellbook
@@ -27,7 +27,15 @@ formula
 	sh
 		echo end: ${list}
 
-
+.write-formula
+	sh amnesia silence write-formula:scroll
+		ls ls/
+		ls ls/
+	
+	foreach scroll
+		sh
+			echo scroll line: ${scroll}
+		
 
 
 
diff --git a/test/spellcast-test.js b/test/spellcast-test.js
index 4a8ddede..4779a4db 100644
--- a/test/spellcast-test.js
+++ b/test/spellcast-test.js
@@ -122,7 +122,7 @@ describe( "'sh' block" , function() {
 		} ) ;
 	} ) ;
 	
-	it( "should substitute variable (aka formula) accordingly" , function( done ) {
+	it( "should substitute variable (aka formula) accordingly in 'sh' block" , function( done ) {
 		
 		cleanup( function() {
 			
@@ -137,6 +137,21 @@ describe( "'sh' block" , function() {
 		} ) ;
 	} ) ;
 	
+	it( "should write a new formula with the output of an 'sh' block" , function( done ) {
+		
+		cleanup( function() {
+			
+			var book = new spellcast.Book( fs.readFileSync( 'spellbook' ).toString() ) ;
+			
+			book.cast( 'write-formula' , function( error )
+			{
+				expect( error ).not.ok() ;
+				expect( getCastedLog( 'write-formula' ) ).to.be( 'scroll line: one\nscroll line: three\nscroll line: two\nscroll line: one\nscroll line: three\nscroll line: two\n' ) ;
+				done() ;
+			} ) ;
+		} ) ;
+	} ) ;
+	
 	/*
 	it( "should launch editor" , function( done ) {