approach to writing functions

[Terry Reedy]

"Bart Nessux" <bart_nessux at hotmail.com> wrote in message
news:c0an8o$g7i$1 at solaris.cc.vt.edu...
> Paul Prescod wrote:
> > If I were you I would post one of these scripts and see if the function
> > and OO fans can make it easier to read or maintain by using structured
> > programming.
>
> OK, here is a script that works w/o OO or functions. It's very useful...
> never fails. It helps sys admins track machines that have mobile users
> who are using DHCP.
>
> #!/usr/bin/python
> #
> # Tested on Linux Machines
> # Run as cron as root
> # May work on OS X too
> #
> # Dec 29, 2003 works on Mac OSX 10.3 like this:
> # chown 'root' && chgrp 'wheel' && chmod '755'
> # place in /usr/bin
> #
>
> from email.MIMEText import MIMEText
> import smtplib
> import os
>
> u = "User" #Change This to user's name.
> f = "admin at XXX.edu"
> t = "admin at XXX.edu"
>
> fp0 = os.popen("/sbin/ifconfig en0 inet", "r")
> fp1 = os.popen("/usr/bin/uptime", "r")
> fp2 = os.popen("/usr/bin/uname -a", "r")
> fp3 = os.popen("/usr/bin/wc -l /etc/passwd", "r")
> msg = MIMEText("-- IFCONFIG --\n\n" + fp0.read() + "\n-- UPTIME --\n\n"
> +  fp1.read() + "\n-- UNAME --\n\n" + fp2.read() + "\n-- PASSWD LC
> --\n\n" + fp3.read())
> fp0.close()
> fp1.close()
> fp2.close()
> fp3.close()
>
> msg["Subject"] = "%s's ifconfig Report" % u
> msg["From"] = f
> msg["To"] = t
>
> h = "smtp.vt.edu"
> s = smtplib.SMTP(h)
> s.sendmail(f, t, msg.as_string())
> s.quit()

Your whole script is a coherent no-argument function:  create and mail a
status message.  C requires you to wrap such within the file as a
syntactically explicit 'main' function.  Python, being against busywork for
the sake of busywork, does not.

The *possible* advantage of doing something like this:

def sendreport():
  <your current code

if __name__ == '__main__':
  sendreport()

is that you could then import the module and use sendreport from another
script.  You might then parameterize it to make some of the constants like
u (user) variable.  You could then do things like

for u in userlist: sendreport(u)

But the value of adding the wrapper and boilerplate and attendant
flexibility depends on your situation.  It also rests on getting the basic
functionality correct.

[OO fans might suggest defining a stat_rep class with a send method, but I
only see that a having much value if you want the learning experience or if
you need to keep unsent messages around.]

As for the code itself.  I would probably use more mnemonic names like
f_inet, f_time, f_name, and f_user, but this is a minor stylistic nit.  I
might also read and maybe close each pipe as created, but maybe you want
the processes to run as close to simultaneous as possible.

Terry J. Reedy