Moving find_exe -> platutils.find_cmd and making is cross platform.

The find_cmd function used to be in ipcluster.py to find executables
on win32.  We need this on all platforms and now we have it!

IPython/iplib.py

@@ -152,7 +152,11 b" def user_setup(ipythondir,rc_suffix,mode='install',interactive=True):"
         printf = lambda s : None
 
     # Install mode should be re-entrant: if the install dir already exists,
-    # bail out cleanly
+    # bail out cleanly.
+    # XXX.  This is too hasty to return.  We need to check to make sure that
+    # all the expected config files and directories are actually there. We
+    # currently have a failure mode if someone deletes a needed config file
+    # but still has the ipythondir.
     if mode == 'install' and os.path.isdir(ipythondir):
         return
 

IPython/kernel/scripts/ipcluster.py

@@ -54,22 +54,10 b' from IPython.kernel.fcutil import have_crypto'
 from IPython.kernel.twistedutil import gatherBoth, wait_for_file
 from IPython.kernel.util import printer
 
-
 #-----------------------------------------------------------------------------
 # General process handling code
 #-----------------------------------------------------------------------------
 
-def find_exe(cmd):
-    try:
-        import win32api
-    except ImportError:
-        raise ImportError('you need to have pywin32 installed for this to work')
-    else:
-        try:
-            (path, offest) = win32api.SearchPath(os.environ['PATH'],cmd + '.exe')
-        except:
-            (path, offset) = win32api.SearchPath(os.environ['PATH'],cmd + '.bat')
-    return path
 
 class ProcessStateError(Exception):
     pass

IPython/platutils.py

@@ -61,6 +61,33 b' def set_term_title(title):'
     _platutils.set_term_title(title)
 
 
+class FindCmdError(Exception):
+    pass
+
+def find_cmd(cmd):
+    """Find full path to executable cmd in a cross platform manner.
+    
+    This function tries to determine the full path to a command line program
+    using `which` on Unix/Linux/OS X and `win32api` on Windows.  Most of the
+    time it will use the version that is first on the users `PATH`.  If
+    cmd is `python` return `sys.executable`.
+
+    Parameters
+    ----------
+    cmd : str
+        The command line program to look for.
+    """
+    if cmd == 'python':
+        return sys.executable
+    try:
+        path = _platutils.find_cmd(cmd)
+    except:
+        raise FindCmdError('command could not be found: %s' % cmd)
+    # which returns empty if not found
+    if path == '':
+        raise FindCmdError('command could not be found: %s' % cmd)
+    return path
+
 #-----------------------------------------------------------------------------
 # Deprecated functions
 #-----------------------------------------------------------------------------

IPython/platutils_dummy.py

@@ -23,3 +23,7 b' ignore_termtitle = True'
 def set_term_title(*args,**kw):
     """Dummy no-op."""
     pass
+
+def find_cmd(cmd):
+    """Find the full path to a command using which."""
+    return os.popen('which %s' % cmd).read().strip()

IPython/platutils_posix.py

@@ -30,3 +30,7 b" if os.environ.get('TERM','') == 'xterm':"
     set_term_title = _set_term_title_xterm
 else:
     set_term_title = _dummy_op
+
+def find_cmd(cmd):
+    """Find the full path to a command using which."""
+    return os.popen('which %s' % cmd).read().strip()

IPython/platutils_win32.py

@@ -41,3 +41,16 b' except ImportError:'
         if ret:
             # non-zero return code signals error, don't try again
             ignore_termtitle = True
+
+def find_cmd(cmd):
+    """Find the full path to a .bat or .exe using the win32api module."""
+    try:
+        import win32api
+    except ImportError:
+        raise ImportError('you need to have pywin32 installed for this to work')
+    else:
+        try:
+            (path, offest) = win32api.SearchPath(os.environ['PATH'],cmd + '.exe')
+        except:
+            (path, offset) = win32api.SearchPath(os.environ['PATH'],cmd + '.bat')
+    return path