posix_access

(PHP 5 >= 5.1.0, PHP 7, PHP 8)

posix_access — Determine accessibility of a file

说明

posix_access(string $filename, int $flags = 0): bool

posix_access() checks the user's permission of a file.

参数

filename

The name of the file to be tested.

flags

A mask consisting of one or more of POSIX_F_OK, POSIX_R_OK, POSIX_W_OK and POSIX_X_OK.

POSIX_R_OK, POSIX_W_OK and POSIX_X_OK request checking whether the file exists and has read, write and execute permissions, respectively. POSIX_F_OK just requests checking for the existence of the file.

返回值

成功时返回 true，或者在失败时返回 false。

示例

示例 #1 posix_access() example

This example will check if the $file is readable and writable, otherwise will print an error message.

<?php

$file = 'some_file';

if (posix_access($file, POSIX_R_OK | POSIX_W_OK)) {
    echo 'The file is readable and writable!';

} else {
$error = posix_get_last_error();

    echo "Error $error: " . posix_strerror($error);
}

?>

参见

posix_get_last_error() - Retrieve the error number set by the last posix function that failed
posix_strerror() - Retrieve the system error message associated with the given errno

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unixguy at earth dot com ¶

10 years ago

It should be noted that this function performs access checks based on the real UID and real GID of the process running PHP.  These aren't necessarily the same as the effective UID and GID.

In other words, it may well be that access() returns “true” for a particular permission, but an fopen() operation which requires the same permission will fail, and vice versa.

Keep that in mind if you use access() for such checks.