C program compilation

I'm a beginner in PostGreSQL and I'm trying to meka my first interface with
a C
program.

Like the documentation says, I'm using the following sentence to compile:

gcc -o output_name -I /usr/include/pgsql -lpq myprogram.c

But, in two diferent Linux servers the answer was:

/usr/lib/libpq.so: undefined reference to `crypt'
collect2: ld returned 1 exit status

I have tryed with millons ways changing the order, including other paths,
etc. ... and
nothing.

If you have the answer or can guide me to some "doc", please response this
mail to:

gbonet(at)bna(dot)com(dot)ar

Thank you !

Gustavo R. Bonet
Buenos Aires
Argentina