what is different unistd.h used for?

[miloody]

Dear all:
I am reading the book "advance programming in UNIX" and it say
unistd.h is posix symbolic constants.
I find all the unistd.h on my environment:
/usr/include$ find ./ -name 'unistd.h'
../asm/unistd.h
../sys/unistd.h
../unistd.h
../bits/unistd.h
../linux/unistd.h
/usr/include$

why there are so many unistd.h and under what circumstances should I
include each of them?
appreciate your help,
miloody

 

[nicolas.sitbon]

Dear all:
I am reading the book "advance programming in UNIX" and it say
unistd.h is posix symbolic constants.
I find all the unistd.h on my environment:
/usr/include$ find ./ -name 'unistd.h'
./asm/unistd.h
./sys/unistd.h
./unistd.h
./bits/unistd.h
./linux/unistd.h
/usr/include$

why there are so many unistd.h and under what circumstances should I
include each of them?
appreciate your help,
miloody

The implementation is not your problem, you should only include
unistd.h
#include <unistd.h>

 

[Noob]

I am reading the book "advance programming in UNIX" and it say
unistd.h is posix symbolic constants.

You'll find POSIX knowledge in a different newsgroup: comp.unix.programmer

 

[miloody]

Hi:

You'll find POSIX knowledge in a different newsgroup: comp.unix.programmer

thanks for your suggestion.
Miloody

 

[Richard Tobin]

I find all the unistd.h on my environment:
/usr/include$ find ./ -name 'unistd.h'
./asm/unistd.h
./sys/unistd.h
./unistd.h
./bits/unistd.h
./linux/unistd.h

The unexpected ones are part of the implementation, either included
in the real <unistd.h> or used by the Linux kernel. You should never
need to consider them for "normal" Posix C programming.

-- Richard

 

[Keith Thompson]

I am reading the book "advance programming in UNIX" and it say
unistd.h is posix symbolic constants.
I find all the unistd.h on my environment:
/usr/include$ find ./ -name 'unistd.h'
./asm/unistd.h
./sys/unistd.h
./unistd.h
./bits/unistd.h
./linux/unistd.h
/usr/include$

why there are so many unistd.h and under what circumstances should I
include each of them?

Questions specifically about unistd.h are best asked in
comp.unix.programmer.

More generally, though, you're probably approaching the problem from
the wrong direction. If you're writing a program that needs to call
a particular function, for example, you should read that function's
documentation to find out what header(s) you should #include.
Start from what you want to do, then find out how to do it, not
the other way around.

On the other hand, curiosity about how your implementation
does things is perfectly valid -- but any answers you get won't
necessarily be useful on other implementations.

 

[Kenny McCormack]

On the other hand, curiosity about how your implementation
does things is perfectly valid -- but any answers you get won't
necessarily be useful on other implementations.

In much the same way as curiosity about the weather on planet Earth is
perfectly valid, but any answers you get won't necessarily be useful on
other planets.

I.e., in case it isn't clear, who the F cares?