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--- codesnippets:filesystemioandstreams [2021/04/22 11:41] – f2b216
+++ codesnippets:filesystemioandstreams [2025/10/08 00:48] (current) – external edit 127.0.0.1
@@ Line 1: / Line 1: @@
+~~DISCUSSION ~~
 ====== Filesystem IO and streams ======
@@ Line 130: / Line 131: @@
         SysIo.hClose hFile
 </code>
-  *example:
     * code, use case of files system<code Haskell>
 import qualified FileSystem as FS
@@ Line 145: / Line 145: @@
             ]
 </code>
-  * compiles ...
+    * compiles, error and warning free, with compiler: GHC 8.10.4, using compiler option -Wall
-  * executes with output as file copy of "a.txt" to "b.txt", ''stdout'', and ''stderr''
+    * executes with output as file copy of "a.txt" to "b.txt", ''stdout'', and ''stderr''
+  * example, with conversions
+    * code:<code Haskell>
+import qualified FileSystem as FS
+import qualified System.IO as SysIo
+import qualified Data.Char as Ch
+main :: IO ()
+main =
+        FS.processData
+            (FS.DataReader (FS.FileInp ".\\test\\a.txt") hGetToUpper)
+            [
+                FS.DataWriter (FS.FileOut ".\\test\\b.txt") SysIo.hPutStr,
+                FS.DataWriter FS.StdOut hPutToLower,
+                FS.DataWriter FS.StdErr SysIo.hPutStr
+            ]
+hGetToUpper :: SysIo.Handle -> IO String
+hGetToUpper h =
+    do
+        s <- SysIo.hGetContents h
+        return (fmap Ch.toUpper s)
+hPutToLower :: SysIo.Handle -> String -> IO ()
+hPutToLower h s = SysIo.hPutStr h (fmap Ch.toLower s)
+</code>
+    * input, file "a.txt"<code>
+The quick brown fox jumps over the lazy dog.
+</code>
+    * output, in terminal:<code>
+the quick brown fox jumps over the lazy dog.
+THE QUICK BROWN FOX JUMPS OVER THE LAZY DOG.
+</code>
+    * output, file "b.txt":<code>
+THE QUICK BROWN FOX JUMPS OVER THE LAZY DOG.
+</code>
+===== ✎ =====
+~~DISCUSSION~~