LinuxQuestions.org - syscalls.h

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- - syscalls.h (https://www.linuxquestions.org/questions/programming-9/syscalls-h-542991/)

Hi,

I have written a program that uses the read() and write() system calls. I want the program to read from a wave file and write to /dev/audio.

Following is the code:

Quote:

#include<stdio.h>
#include "syscalls.h"

int main()
{
int a,b;
char c[2];

((a=read(0,c,2))==2) ? write(1,c,2): ((a==0) ? printf("EOF\n"): printf("error in reading\n"););
return(0);
}

My questions are these:

1) Is there a std header file called syscalls.h
2) When I compile this program using gcc, I get the following error:

Quote:

gcc: no input files

would this be the right command to give:

gcc wavread2.c xyz.wav -o wavread2.o

Thanks,
Ashlesha.

alright sorted out the error with the no input files...
but syscalls.h doesnt exist!

You don’t need to use the system calls directly, just use the C wrappers that come with your C library. In short, do an “#include <unistd.h>” to get the read() and write() functions (taken from man pages). You don’t need any explicit linking since they are part of the standard C library.

If you for some reason, wish to use the system calls directly (or, more correctly, with a very thin wrapper), try something like:

Code:

#include <stdio.h>

#include <sys/syscall.h>



static inline ssize_t write(int fildes, const void *buf, size_t nbyte)

{

        return syscall (__NR_write, fildes, buf, nbyte);

}



static inline ssize_t read(int fildes, void *buf, size_t nbyte)

{

        return syscall (__NR_read, fildes, buf, nbyte);

}



int main()

{

        int a,b;

        char c[2];



        ((a=read(0,c,2))==2) ? write(1,c,2): ((a==0) ? printf("EOF\n"): printf("error in reading\n");

        return(0);

}