gistfile1.sh

# I want to *snoop* the stdout(1) and stderr(2) of the process named 'ntfsresize'
# (run as root)
strace -p $(pidof "ntfsresize") -e trace=write 2>&1 | grep 'write(1'
       
# Explanation:
#
#      -p $(pidof "ntfsresize") 
#      Apply strace to the process named "ntfsresize"
#      If you want to trace a bash script, use instead $(pidof -x "script-name.sh")
#
#      -e trace=write   
#      Trace only the WRITE system calls
#      Keep in mind that 
#              write(1,... will write to STDOUT
#              write(2,... will write to STDERR
#              write(3-and-up,... will write to other filedescriptors (files, sockets, or whatever the program opens)
#      Doing "-e trace=write" is the same as "-e write"      
#
#      2>&1 | grep 'write(1'
#      The strace program shows sends its output to stderr, we then join its stderr into stdout and finally pipe it 
#      to the grep. We need to join stderr to stdout because pipes normally only pass stdout, not stderr.
#      The grep grabs the straced write calls directed to stdout "write(1,..." 
#

C Evans comment gave it a big improvement :)