Initial commit

LICENSE

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+Copyright (C) 2015 Jack-Benny Persson <jack-benny@cyberinfo.se>
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program; if not, write to the Free Software
+Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+

README.md

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+# Subcalc #
+Subcalc is a small Python program I wrote as a free assigment during a Python
+class at EC Utbildning. The program takes a netmask in slash notation as
+argument and gives back the netmask in dotted decimal notation.
+
+## Usage ##
+```
+Usage: subcalc.py <netmask in slash-notation>
+Example: subcalc.py 24
+```
+
+## License ##
+Subcalc is made by Jack-Benny Persson and is released under GNU GPL version 2.

subcalc.py

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+#!/usr/bin/env python
+# -*- coding:utf-8 -*-
+import sys
+
+def subcalc(slash):
+    """    Subcalc is a simple function to convert a slash-notation netmask 
+        into a dotted decimal notation netmask.
+
+        Usage: subcalc(netmask)
+        Example: subcalc (24)
+                 will return 255.255.255.0
+
+        Note: As input to subcalc, enter only the number, not the leading slash.
+              If an invalid slash-notation netmask is sent to subcalc.
+              it will return -1
+    """
+    # Check if the value is an int, if it's not then quit and return -1
+    if isinstance(slash, int) == False:
+        return -1
+        sys.exit()
+    # Check the size of the netmask, if bogus, then quit end return -1
+    if slash < 0 or slash > 32:
+        return -1
+        sys.exit()
+
+    zeroes = "0" * (32-slash) # Fill up "the rest" with zeroes
+    binNum = "1" * slash # Fill up the binary string with ones
+    binNum = binNum + zeroes # Put together the ones and the zeroes (tot = 32)
+    sub = "" # Initalize sub-variable
+
+    # Divide the binary string into four groups
+    group = []
+    group.append(binNum[0:8])
+    group.append(binNum[8:16])
+    group.append(binNum[16:24])
+    group.append(binNum[24:])
+
+    # For each group, convert to decimal type and end with a dot and append
+    # the result to the sub-variable
+    for i in group:
+        sub += (str(int(i, 2))+".")
+    return sub.rstrip(".") # Strip of the last dot
+
+def main():
+    # A simple implementation of the subcalc-function above
+    # Takes one command-line argument (the netmask)
+    if len(sys.argv) < 2: 
+        print "Usage: subcalc.py <netmask in slash-notation>"
+        print "Example: subcalc.py 24"
+        sys.exit()
+    arg = int(sys.argv[1]) # Have to typecast here since arguments are strings
+    print subcalc(arg)
+    
+    #help(subcalc)
+
+if __name__=='__main__':
+    main()