UNIX for Advanced & Expert Users

#!/bin/sh
pwdfile =/users/home/sadmin/pwd.txt ( contains the password for my account ) 
 
 psh su - sadmin
< cat $pwdfile 
 
/users/siebelserver/siebsrvr
./stop_server all
 
do something
/users/siebelserver/siebsrvr
./start_server all

#!/bin/sh
# You can't just put a comment anywhere and expect the
# script to still work.  At least put a # before them.
#  ( contains the password for my account ) 
gaping_security_hole=/users/home/sadmin/hackers_dont_read_this_file_pretty_please.txt

# 1) < > are for files, not processes.  'cat < "$pwdfile"' may have been what
#     you meant, I'm not sure.
# 2) Your redirection wasn't even on the same line, so couldn't have worked.
#     That's probably why it was hanging.
# 3) You don't need to use cat here.
# 4) su isn't supposed to work that way.  It's designed not to accept
#     hardcoded passwords for security reasons.  You should NOT be keeping
#     plaintext passwords around for any reason.
# 5) Even if you manage to cudgel su into reading the password from file
#     somehow, it won't execute the statements following it.  It runs
#     separately, it doesn't extend the permissions of your existing script.
#
#     Usually, you either run su interactively, or feed it a command to run.
#     Don't embed su in script files, use su to call a script file.
su - sadmin -c "/path/to/script/file" < "$gaping_security_hole"

# ...or better yet, use sudo.  It can be configured very exactly.  Your
# sysadmin can tell it to let you, and only you, to run this and only this 
# command, as that and only that user, with no password.
sudo -u sadmin /path/to/script/file