Add support for plain output

Make ASCII escape characters optional. Colored output can be deactivated with
`--plain` or the environment variable `DOXEC_COLOR=0'. The environment variable
can be overridden with `--color`.

bin/doxec

@@ -3,6 +3,7 @@
 import argparse
 import doxec
 import sys
+import os
 
 if __name__ == "__main__":
     parser = argparse.ArgumentParser(
@@ -21,6 +22,12 @@ if __name__ == "__main__":
     parser.add_argument("--short", action="store_true",
         help="Suppresses the standard output of operations.")
 
+    parser.add_argument("--plain", action="store_true",
+        help="Do no use ASCII control characters, equal to DOXEC_COLOR=0.")
+
+    parser.add_argument("--color", action="store_true",
+        help="Force the usage ASCII control characters. This overrides DOXEC_COLOR=0.")
+
     parser.add_argument("documents", metavar="DOCUMENT", nargs="+", default=[],
         help="A document from which the code examples should be parsed and "
             "executed")
@@ -33,19 +40,30 @@ if __name__ == "__main__":
 
     parser = doxec.parser[args.syntax]
 
+    plain = args.plain or \
+        ("DOXEC_COLOR" in os.environ and os.environ["DOXEC_COLOR"] == '0')
+
+    plain = plain and (not args.color)
+
+
     print("Doxec -- Copyright (c) 2017 Frank Sauerburger")
 
     # Loop over documents
     for doc_path in args.documents:
         doc = doxec.Document(doc_path, syntax=parser)
-        monitor = doxec.Monitor(doc_path, short=args.short)
+        monitor = doxec.Monitor(doc_path, short=args.short, color=not plain)
         doc.run(monitor=monitor)
 
     # Print summary
     print("-"*80)
     color = "\033[31m" if monitor.fail_count > 0 else "\033[32m"
 
-    print(color + "Failed: %5d\033[0m" % monitor.fail_count)
+    if not plain: print(color, end="")
+    print("Failed: %5d" % monitor.fail_count, end="")
+    if not plain: print("\033[0m", end="")
+    print()
+
+
     print("Total:  %5d" % monitor.total_count)
 
     # Return code equals number of failed operations

doxec/__init__.py

@@ -440,7 +440,7 @@ class Monitor(metaclass=abc.ABCMeta):
     of a fail and total counter.
     """
 
-    def __init__(self, path, short=False):
+    def __init__(self, path, short=False, color=True):
         """
         Initializes the monitor. A new monitor should be used for each file.
         The short argument, defines whether the standard output of operations
@@ -449,6 +449,7 @@ class Monitor(metaclass=abc.ABCMeta):
 
         self.full_path = os.path.abspath(path)
         self.short = short
+        self.color = color
 
         self.first_line = False
 
@@ -461,7 +462,10 @@ class Monitor(metaclass=abc.ABCMeta):
         This method set the internal values and caches the lines and the
         operation.
         """
-        print("\033[2K\033[0G\033[33m%s:%-5d %s ... \033[39;49m" % (self.full_path, line, operation), end="")
+        if self.color: print("\033[2K\033[0G\033[33m", end="")
+        print("%s:%-5d %s ... " % (self.full_path, line, operation), end="")
+        if self.color: print("\033[39;49m", end="")
+
         self.pending_line_break = True
         self.line = line
         self.operation = operation
@@ -475,7 +479,10 @@ class Monitor(metaclass=abc.ABCMeta):
         """
         self.total_count += 1
         if error is None:
-            print("\033[2K\033[0G\033[32m%s:%-5d %s ... done\033[39;49m" % (self.full_path, self.line, self.operation))
+            if self.color: print("\033[2K\033[0G\033[32m", end="")
+            print("%s:%-5d %s ... done" % (self.full_path, self.line, self.operation), end="")
+            if self.color: print("\033[39;49m", end="")
+            print()
         else:
             self.fail_count += 1
             if self.pending_line_break:
@@ -487,8 +494,13 @@ class Monitor(metaclass=abc.ABCMeta):
             else:
                 args = [str(error)]
             for error_line in args:
-                print("\033[31m%s" % str(error_line))
-            print("\033[31m%s:%-5d %s ... failed\033[39;49m" % (self.full_path, self.line, self.operation))
+                if self.color: print("\033[31m")
+                print(str(error_line))
+
+            if self.color: print("\033[31m", end="")
+            print("%s:%-5d %s ... failed" % (self.full_path, self.line, self.operation), end="")
+            if self.color: print("\033[39;49m", end="")
+            print()
 
     def log(self, lines):
         """