Linux Header Files (c programming)

[Benjamin Honsinger]

Hi people! How do I find out if I have a certain header file on my computer? I
am trying to compile a program that uses header files like termios.h, fcntl.h,
sys/stat.h and sys/types.h
I don't know if these are standard header files that are on my computer or not.
I don't think that termios.h is on my computer, because I get the following
errors.
[benh at mandrake prgm]$ gcc openserialport.c
openserialport.c: In function `OpenSerialPort':
openserialport.c:28: `termios' undeclared (first use in this function)
openserialport.c:28: (Each undeclared identifier is reported only once
openserialport.c:28: for each function it appears in.) 
openserialport.c:28: parse error before `newtio' 
openserialport.c:42: `newtio' undeclared (first use in this function)
[benh at mandrake prgm]$
Thanks in advance!
	- Benjamin - 
PS If you're really feeling nice, ask me to send you openserialport.c so you
can help me out with writing it....