From: Vincent Roqueta <vincent.roqueta@ext.bull.net>
Subject: Re: NFS and C Language
Date: Fri, 9 Dec 2005 15:24:39 +0100
Message-ID: <200512091524.39616.vincent.roqueta@ext.bull.net>
References: <ADEFIEOLGCCFDKBLPHKEIEEJCDAA.e_rln@yahoo.co.in> <200512091231.26341.vincent.roqueta@ext.bull.net> <43999068.3080500@redhat.com>
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Le Vendredi 09 D=E9cembre 2005 15:10, Peter Staubach a =E9crit=A0:
> Vincent Roqueta wrote:
> >Le Vendredi 09 D=E9cembre 2005 12:12, RLN a =E9crit :
> >>Hi!
> >>
> >>
> >>I want to write simple C language program to read and write a file in N=
=46S
> >>file system.
> >>
> >>Please give a link or advice to write a program using C language.
> >>
> >>Also help for which calls I have to use.
> >
> >You access NFS as other file systems...
> >Generic C howto about files manipulations works for NFS.
> >
> >Vincent
> >
> >
> >_______________________
> >#include <stdio.h>
> >#include <string.h>
> >#include <sys/types.h>
> >#include <sys/stat.h>
> >#include <fcntl.h>
> >
> >
> >int main(int argc, char **argv){
> >    char path[]=3D"/path/to/the/testfile";
> >    char string[]=3D"hello world!";
> >    int fd;
> >
> >    fd=3Dopen(path,O_WRONLY|O_CREAT);
> >    if(fd<0){
> >        perror("Open");
> >        return 0;
> >    }
> >    write(fd, string,strlen(string));
> >    return 0;
> >}
>
> Actually, this little program may or may not work on an NFS mounted file
> system.  It contains a bug in that the open(2) system call takes three
> arguments and the third, the mode, is used when O_CREAT is specified and
> the file does not already exist.  If the random bits, which the kernel
> uses because the mode was not actually specified, are wrong, like for
> example require mandatory locking, then the write(2) call may fail.
> Also, the write(2) call returns whether or not it succeeded and how much
> data was written.  The close(2) call, which was not explicitly coded,
> but should have been, is also used to return whether any error occurred
> while trying to write data to the NFS server.
Right...
You can add I return 0 even if the program fails...

I have taken a little less than 3 minutes to write this little example :)
I hope C howto examples will be better :)

Vincent


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