From: simonmar <unknown>
Date: Tue, 2 Jul 2002 10:31:35 +0000 (+0000)
Subject: [project @ 2002-07-02 10:31:35 by simonmar]
X-Git-Tag: nhc98-1-18-release~957
X-Git-Url: http://git.megacz.com/?a=commitdiff_plain;h=7362fdb061655b3b202e65ae1abe67adc959ddae;p=ghc-base.git

[project @ 2002-07-02 10:31:35 by simonmar]
Documentation for system
---

diff --git a/System/Cmd.hs b/System/Cmd.hs
index 0be8008..4bd07af 100644
--- a/System/Cmd.hs
+++ b/System/Cmd.hs
@@ -8,7 +8,7 @@
 -- Stability   :  provisional
 -- Portability :  portable
 --
--- Executing a command.
+-- Executing an external command.
 --
 -----------------------------------------------------------------------------
 
@@ -28,17 +28,26 @@ import GHC.IOBase
 -- ---------------------------------------------------------------------------
 -- system
 
--- Computation `system cmd' returns the exit code
--- produced when the operating system processes the command `cmd'.
+{-| 
+Computation @system cmd@ returns the exit code
+produced when the operating system processes the command @cmd@.
 
--- This computation may fail with
---   PermissionDenied 
---	The process has insufficient privileges to perform the operation.
---   ResourceExhausted
---      Insufficient resources are available to perform the operation.  
---   UnsupportedOperation
---	The implementation does not support system calls.
+This computation may fail with
 
+   * @PermissionDenied@: The process has insufficient privileges to
+     perform the operation.
+
+   * @ResourceExhausted@: Insufficient resources are available to
+     perform the operation.
+
+   * @UnsupportedOperation@: The implementation does not support
+     system calls.
+
+On Windows, 'system' is implemented using Windows's native system
+call, which ignores the @SHELL@ environment variable, and always
+passes the command to the Windows command interpreter (@CMD.EXE@ or
+@COMMAND.COM@), hence Unixy shell tricks will not work.
+-}
 system :: String -> IO ExitCode
 system "" = ioException (IOError Nothing InvalidArgument "system" "null command" Nothing)
 system cmd =