Re: "Learning Perl" book, Chapter 1 example: open MAIL, "|mail email_address" doesn't workemail_address" doesn't work

[Robin]

On Monday, June 9, 2003, at 02:32  am, Dan Mills wrote:
On Monday, June 9, 2003, at 02:45  am, drieux wrote:
On Sunday, Jun 8, 2003, at 08:58 US/Pacific, Robin wrote:
On Thursday, June 5, 2003, at 03:36  am, Dan Mills wrote:
[..]
It's unfortunate that mail exits with 0, however. .........It isn't 
mail's fault, though.  sendmail returns with 0 as well.
it's a UNIX C-ism which return 0 instead - historically any other 
return value would be an error code
mail, mailx, et al 'ran successfully' - and hence
should exit with '0' - because they ran successfully.
Yes, but that's the point.  It returns 0, even though it clearly 
failed to send the mail.


the point being that certain Unix command line tools don't use a 
boolean ('1' = yes, '0'= no) as a way of codifying success for reasons 
which are connected to programming C on Unix, the logic of which can 
still be seen in certain man pages.

So the real question is what success does that '0' represent?

(lifted from a SunOS man page for mail at 
http://bama.ua.edu/cgi-bin/man-cgi?mail+1):
EXIT STATUS
     The following exit values are returned:

     0     Successful completion when the user had mail.

     1     The user  had  no  mail  or  an  initialization  error
           occurred.
You got mail apprently - did you check? :-) In all fairness the OSX 
manpages don't talk about return values, I suppose they assume you 
wouldn't be running mail except in interactive mode. A fair assumption 
- there are ways to forward/send mail which don't use either mail or 
sendmail, (one of them is  Net::SMTP).

But I feel the poster's real question is about why the example from the 
official bible for perl learners doesn't do what the book says it 
should - before OSX, Unix systems always had a SMPT/POP mail daemon 
built into the system, which as surely as night follows day would be 
active and fully functioning. In OSX the daemon is not configured by 
default and requires considerable tweaking to be kept running across 
software updates due to the Apple installers resetting disk 
permissions. In short the Learning Perl example doesn't even consider 
the fact that there might not be a working mail daemon, which is 
unthinkable on all flavours of Unix except OSX.

If you have a working mail daemon then:
*in mail.app you could set the SMTP and POP servers to localhost 
(127.0.0.1)
*other people would be able to send mail through your computer onto the 
internet

and checking in the terminal checking for a process called sendmail 
would get you this:
[blue:~] robin% ps -aux | grep sendmail
smmsp  1381   0.0  0.3     2204    924  p1  S+   12:33PM   0:01.73 
sendmail
robin  1387   0.0  0.1     1416    312 std  S+   12:34PM   0:00.01 grep 
sendmail

otherwise you'll only see the grep command looking for a process called 
sendmail:
robin% ps -aux | grep sendmail
robin  1389   0.0  0.0     1116      4 std  R+   12:35PM   0:00.00 grep 
sendmail

you can of course put this into a perl script that checks if sendmail 
is running:

#!/usr/bin/perl -w

#=========== declare includes =============

use strict;
use diagnostics-verbose;
#========== declare variables =============

my($test);

#============= script body ================
$test=`ps -aux | grep sendmail`;
print "Sendmail running\n" if $test=~/^smmsp/;
print "Sendmail not running\n" if $test!~/^smmsp/;
hth

Robin