1 files changed, 19 insertions, 5 deletions

diff --git a/csv_tool b/csv_tool
index 674c51c..e747462 100755
--- a/csv_tool
+++ b/csv_tool
@@ -9,6 +9,7 @@ import defapp
 
 import csv
 import operator
+import os.path
 from collections import defaultdict as defdict
 
 o = optparse.make_option
@@ -22,6 +23,9 @@ opts = [
     o('-c', '--column', action='store', dest='col', type='int',
       help='The column on which to operate.'),
 
+    o(None, '--write-to-file', action='store_true', dest='write_to_file',
+      help='Write the output of operation xyz on file abc.csv to xyz_abc.csv.'),
+
 #     o(None, '--true', action='store_true', dest='truth',
 #       help='A boolean flag value.'),
 
@@ -30,8 +34,9 @@ opts = [
     ]
 
 defaults = {
-    'col'          : 0,
-    'col_xcgh'     : [],
+    'col'           : 1,
+    'col_xcgh'      : [],
+    'write_to_file' : False,
     }
 
 def make_vector_op(op):
@@ -109,9 +114,11 @@ def select_by_key(rows, col, cast=None):
 class CsvApp(defapp.App):
     def __init__(self):
         defapp.App.__init__(self, opts, defaults)
+        # fixup human-friendly offsets
         self.options.col -= 1
-        self.options.col_xchg = [(x - 1, y - 1) for (x, y) in
-                                 self.options.col_xchg]
+        if self.options.col_xchg:
+            self.options.col_xchg = [(x - 1, y - 1) for (x, y) in
+                                     self.options.col_xchg]
 
     def transform(self, make_iterator, ordered=True):
         """Average all rows with the same key in a given column."""
@@ -129,7 +136,14 @@ class CsvApp(defapp.App):
                 else:
                     rows = make_iterator(rows)
                 # write out
-                csv.writer(self.outfile()).writerows(rows)
+                outfile = self.outfile()
+                if self.options.write_to_file:
+                    (dir, file) = os.path.split(fn)
+                    fn = os.path.join(dir, self.args[0] + '_' + file)
+                    outfile = open(fn, 'w')
+                csv.writer(outfile).writerows(rows)
+                if self.options.write_to_file:
+                    outfile.close()
             except IOError, ex:
                 self.err("%s:%s"  % (fn, str(ex)))
             except IndexError, ex: