I have a problem in Linux programming about file read and write

[thlgood]

If file is not exist,create it and write a string into it, else write a string into this file.

but the problem is that open() return a bad file descriptor if this file is exist.

code:

/*
Linux Open() example source code
Author:        Yucoat(www.yucoat.com)
Data:        2011-10-31
Version:    v0.1
ChangeLog:    Create This program        2011-20-31
 */
#include <fcntl.h>        //for open
#include <errno.h>        //for errno
#include <stdio.h>


int main()
{
    int fd;


    if ((fd = open(    "./Name",                                        //File name
                    O_WRONLY|O_EXCL|O_APPEND|O_CREAT,                //Mod
                    S_IRUSR|S_IWUSR|S_IRGRP|S_IWGRP|S_IROTH)) < 0)    //Access
    {
        perror("open");
        return -1;
    }


    if (write(fd, "Yucoat\n", 7) != 7)
        perror("Write");
    close (fd);
    return 0;
}

Thx for every body!I'm very sorry for my bad english!

[quzah]

but the problem is that open() return a bad file descriptor if this file is exist.

Of course it does. You told it to:

    if ((fd = open(    "./Name",                                        //File name
                    O_WRONLY|O_EXCL|O_APPEND|O_CREAT,                //Mod

When in doubt, read the man page.


Quzah.

[thlgood]

Yes I read it.

But it's a big challenge for me to understand some man pages...

Thx

[rags_to_riches]

This

O_EXCL error if create and file exists

seems pretty crystal clear to me, considering your problem is

the problem is that open() return a bad file descriptor if this file is exist.