PHP umask Function

last modified April 3, 2025

The PHP umask function sets the default permission mask for files and directories. It affects permissions of newly created files and directories.

Basic Definition

The umask function changes the current umask (user mask) value. It takes an octal value representing permissions to be disabled by default.

Syntax: umask(?int $mask = null): int. The function returns the previous umask value. Without parameters, it returns current umask without changing it.

Basic umask Example

This shows how to set a basic umask and check its effect on file creation.

basic_umask.php

<?php

declare(strict_types=1);

$old_mask = umask(0); echo “Old umask: " . decoct($old_mask) . “\n”;

$file = fopen(“test.txt”, “w”); fclose($file);

$perms = fileperms(“test.txt”); echo “File permissions: " . decoct($perms & 0777) . “\n”;

umask($old_mask); // Restore original umask unlink(“test.txt”);

This sets umask to 0, allowing full permissions (777). The created file will have permissions based on the umask. We restore the original umask afterward.

Restrictive umask Example

This demonstrates how a restrictive umask affects new file permissions.

restrictive_umask.php

<?php

declare(strict_types=1);

$old_mask = umask(0077); // Remove all group/other permissions echo “Old umask: " . decoct($old_mask) . “\n”;

$file = fopen(“secure.txt”, “w”); fclose($file);

$perms = fileperms(“secure.txt”); echo “File permissions: " . decoct($perms & 0777) . “\n”;

umask($old_mask); // Restore original umask unlink(“secure.txt”);

With umask 0077, new files will have permissions 600 (rw——-). The umask value is subtracted from the default permissions (666 for files).

Directory Creation with umask

This example shows how umask affects directory permissions differently.

directory_umask.php

<?php

declare(strict_types=1);

$old_mask = umask(0022); // Common default umask echo “Old umask: " . decoct($old_mask) . “\n”;

mkdir(“new_directory”);

$perms = fileperms(“new_directory”); echo “Directory permissions: " . decoct($perms & 0777) . “\n”;

umask($old_mask); // Restore original umask rmdir(“new_directory”);

With umask 0022, new directories will have permissions 755 (rwxr-xr-x). The umask subtracts from default directory permissions (777). Execute bits remain.

Temporary umask Change

This shows how to temporarily change umask for specific operations.

temporary_umask.php

<?php

declare(strict_types=1);

function createSecureFile(string $filename): void { $old_mask = umask(0077); $file = fopen($filename, “w”); fclose($file); umask($old_mask); }

createSecureFile(“private.txt”); $perms = fileperms(“private.txt”); echo “File permissions: " . decoct($perms & 0777) . “\n”;

unlink(“private.txt”);

The function temporarily sets a restrictive umask for file creation. The umask is automatically restored after file creation, preventing global side effects.

Checking Current umask

This example demonstrates how to check the current umask without changing it.

check_umask.php

<?php

declare(strict_types=1);

$current_umask = umask(); echo “Current umask: " . decoct($current_umask) . “\n”;

// Create a test file to see actual permissions $file = fopen(“testfile.txt”, “w”); fclose($file);

$perms = fileperms(“testfile.txt”); echo “Actual file permissions: " . decoct($perms & 0777) . “\n”;

unlink(“testfile.txt”);

Calling umask() without parameters returns the current umask value. The actual file permissions will be 666 minus the umask value (for files).

Best Practices

• Restore umask: Always restore original umask after changes.

• Octal notation: Use octal numbers (e.g., 077) for clarity.

• Scope: Limit umask changes to smallest necessary scope.

• Security: Consider security implications of permissions.

• Document: Document umask changes in team environments.

Source

PHP umask Documentation

This tutorial covered the PHP umask function with practical examples showing its usage for permission control in filesystem operations.

Author

My name is Jan Bodnar, and I am a passionate programmer with extensive programming experience. I have been writing programming articles since 2007. To date, I have authored over 1,400 articles and 8 e-books. I possess more than ten years of experience in teaching programming.

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