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

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:

Code:

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/*
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;
}

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

Quote:

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Originally Posted by thlgood

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

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Of course it does. You told it to:

Quote:

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Originally Posted by thlgood

Code:

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

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When in doubt, read the man page.


Quzah.

Yes I read it.

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

Thx

This

Quote:

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O_EXCL error if create and file exists

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seems pretty crystal clear to me, considering your problem is

Quote:

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

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