为什么fopen与x模式给我“无法打开流：没有这样的文件或目录”

问题描述：

I want to use mode x because as I can see from php.net that if the file exists it gives and error and also return false, and if not it creates it (also the directory's).

This is the script. It is located in www.ex.com/s/index.php

$urlParts = "/img/logo.png";
$fp = fopen( __DIR__ . $urlParts, "x" );

This should create logo.png (and also create the directory /img/) if it does not exist...but it is not working like this.

Anyone can help? Thanks!

我想使用模式x，因为我可以从php.net看到，如果文件存在，它会给出错误并返回false，如果没有，则返回false（也是目录的）。 p>

这是脚本。它位于www.ex.com/s/index.php

$urlParts =“/ img / logo.png”; 
n $ fp = fopen（__DIR__。  $ urlParts，“x”）; 
  code>  pre> 
 
 如果它不存在，这应该创建logo.png（并创建目录/ img /）...但是 它不像这样工作。   p> 
 
 
任何人都可以提供帮助吗？ 谢谢！ p> 
  div>

答

fopen("/img/logo.png","x");

It will not create the img directory in any case. If the directory does not exist, then it will always throw this warning.

Warning: fopen(/img/logo.png): failed to open stream: No such file or directory

fopen("logo.png","x");

If logo.png does not already exist, then it will create it without any warning. If logo.png already exists, then it will always throw this warning.

Warning: fopen(logo.png): failed to open stream: No such file or directory

fopen("","x") is equivalent to specifying O_EXCL|O_CREAT flags for the underlying open(2) system call. Now let me help you understand why it happens.

In POSIX, The O_CREAT flag causes a file to be created if it doesn't already exist. If you include the O_CREAT flag, you must also pass a third argument to open to designate the permissions. If you want to avoid writing over an existing file, use the combination O_CREAT | O_EXCL. This combination returns an error if the file already exists.

C program using POSIX

#include <fcntl.h>
#include <sys/stat.h>
int open(const char *path, int oflag, ...);

Conclusion: So we will use the "x" mode only when we want to avoid writing over an existing file.

为什么fopen与x模式给我“无法打开流：没有这样的文件或目录”

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