ssh from shell script

i m trying to write a script which works as follow.
machine A , where my script is
machine B , the machine where i m trying to ssh

while in A, i'm trying to ssh B, and check if file test.c exist.
if exist, error msg will be displayed.

---------------------------------------------
ssh b.example.com
if [ -f /home/test.c ]; then
echo "file existing! " 1>&2
echo "Program terminating!" 1>&2
exit 1
fi
---------------------------------------------

but this alone is not working.
once i ssh, i'm considering entering machine B.
i would like the code below to work background in machine B, while i'm waiting for the result at machine A terminal.

may i know how i should code this?

can you put the code you want to run on machine B in a script and just call it with the -c switch to ssh? otherwise there's tools that can send info (Expect, maybe?) that you can look up and use

that is an idea too.
thanks.
i will try it out, but if the command i want to run in machine B is just one line or two, i hope that i do not need to script it.

by the way, i got the solutions as follow.
if ssh b.com ' [ -f file.c ] ' ; then
echo "error"

quote the command i want it to do with single quotations.


thanks for the idea

Thanks for the code, this can be used for more more command with more condition.