Musings

A recent article in Red Hat Magazine by Noah Gift and Grig Gheorghiu called “This isn’t your grandpappy’d dd command demonstrated how to use Python, the dd utility and the Google Chart API to produce a bar chart showing throughput at different block sizes. However the output from the Python script was not the actual graph but a URL which you then had to paste into a Web browser to view the resulting chart.

I though this script would be useful but did not want to have to cut and paste a URL into a Web browser so I decided to eliminate that step.

This Python script is loosely based on their script but uses the Python urllib libraries to connect to Google Charts to generate a PNG image file which is subsequently displayed using pyGTK+ routines. #!/usr/bin/env python import sys import os import commands import re from optparse import OptionParser import urllib import urllib2 import pygtk pygtk.require(’2.0′) import gtk class DisplayGraph: def delete_event(self, widget, event, data=None):    return False def destroy(self, widget, data=None):    gtk.main_quit() def __init__(self):    self.window = gtk.Window(gtk.WINDOW_TOPLEVEL)    self.window.connect(“delete_event”, self.delete_event)    self.window.connect(“destroy”, self.destroy)    self.window.set_border_width(10)    self.window.set_position(gtk.WIN_POS_CENTER)    self.window.set_title(“Disk Throughput”)    pixbuf = gtk.gdk.pixbuf_new_from_file(“/tmp/dd.png”)    os.remove(“/tmp/dd.png”)    self.image = gtk.Image()    self.image.set_from_pixbuf(pixbuf)    self.image.show()    self.window.add(self.image)    self.window.show() def main(self):    gtk.main() class GoogleChart: def __init__(self):    self.gchart_url = “http://chart.apis.google.com/chart?”    self.gchart_type = “cht=bvs”    self.gchart_title = “&chtt=”    self.gchart_data = “&chd=t:”    self.gchart_labels = “&chxl=0:|”    self.gchart_size = “&chs=400×250″    self.gchart_axis_labels = “&chxt=x,y,x,y”    self.gchart_axis_position = “&chxp=2,50|3,50″    self.gchart_bar_settings = “&chbh=30,15″ def title(self,title):    self.gchart_title = self.gchart_title + title def write(self, data, labels, max_t):     self.gchart_data = self.gchart_data + data.rstrip(‘,’)     self.gchart_labels = self.gchart_labels \       + labels + “2:|Block%20Size|3:|Mb/s”     self.gchart_axis_range = “&chxr=1,0,” + str(max_t+10.0)     self.gchart_scaling = “&chds=0,” + str(max_t+10.0)     self.gchart_url += self.gchart_type \       + self.gchart_title + self.gchart_size     self.gchart_url += self.gchart_bar_settings \       + self.gchart_data + self.gchart_labels     self.gchart_url += self.gchart_axis_labels \       + self.gchart_axis_position     self.gchart_url += self.gchart_axis_range \       + self.gchart_scaling    opener = urllib2.urlopen(self.gchart_url)    if opener.headers['content-type'] != ‘image/png’:       raise BadContentTypeException(‘Server responded’ \          ’with a content-type of %s’ \          % opener.headers['content-type'])    open(“/tmp/dd.png”, ‘wb’).write(opener.read()) def get_disk_throughput(device, blocksize):    blocksize = str(blocksize) + ‘k’    cmd = “dd if=/dev/zero of=%s bs=%s” % (device,blocksize)    output = commands.getoutput(cmd)    throughput = 0    unit = “”    for line in output.split(‘n’):       s = re.search(‘ copied,.*, (\S+) (\S+)$’, line)       if s:          throughput = s.group(1)          unit = s.group(2)          break    return (throughput, unit) if __name__ == “__main__”:    usage = “Usage: %prog options”    parser = OptionParser(usage=usage)    parser.add_option(“-d”, “–device”, dest=”device”, \       help=”Device to use. Disk data will be overwritten!”)    (options, args) = parser.parse_args()    device = options.device    if not device:       parser.print_help()       sys.exit(1)