ps detects context?

[Alan Mead <adm ipat com>]

I have a perl script.  To make sure it is running, I do a 'ps aux' and see 
something like on my screen:

[amead hera amead]$ ps aux
USER       PID %CPU %MEM   VSZ  RSS TTY      STAT START   TIME COMMAND
root         1  0.0  0.1  1104   72 ?        S    Jul05   5:50 init [3]
...
root     22461  0.1  3.0  2840 1904 pts/1    S    13:07   0:01 perl -w 
/usr/sbin/sendreports
...

But if I try to pipe the output into grep looking for 'sendreports' I get 
nothing.  If I grep for perl, I get part of the command line:

[amead hera amead]$ ps aux | grep -i sendreport
[amead hera amead]$ ps aux | grep -i perl
root     22461  0.1  3.0  2840 1904 pts/1    S    13:07   0:01 perl -w 
/usr/sbin
amead    22570  0.0  0.6  1164  428 pts/2    S    13:28   0:00 grep -i perl

Why does ps truncate it's output?

The -w option does give the complete width but I'm curious why the output 
varies between depending on whether it's going to the screen to a pipe.  I 
sense the possibility that I could learn something here...

-Alan
---
Alan Mead, Ph.D.  /  Research Scientist  /  adm ipat com
Institute for Personality and Ability Testing
1801 Woodfield Dr  /  Savoy IL 61874 USA
217-352-4739 (v)  /  217-352-9674 (f)