EACCES

EACCES is a POSIX errno value that indicates a permission denied condition. It is returned by the kernel or standard library when a process attempts an operation for which it does not have the required access rights, such as opening, reading, writing, or executing a file, or accessing a directory component without the necessary permissions.

Common scenarios include trying to open a read-only file for writing, attempting to execute a program or script without the execute bit set, or trying to traverse a directory path for which the process lacks execute (search) permission on one of the components. EACCES is a permission-related error distinct from errors caused by a missing file (ENOENT) or an unsupported operation (EPERM in some cases). In practice, a program may receive EACCES from system calls like open, access, stat, or chown when the effective user ID does not grant the requested access.

Cross-platform behavior varies. In POSIX environments EACCES is well defined, typically with a numeric value of 13 on Linux and many other systems. On Windows, similar permission issues may be reported through different error codes, often translated by language runtimes into a generic access-denied message that resembles EACCES in meaning.

Handling EACCES involves checking the errno after a failure, logging or displaying a user-friendly message, and adjusting permissions or ownership as appropriate. Remedies include changing file or directory permissions (chmod, chown), configuring access control lists, ensuring the correct interpreter or mount options (such as noexec) are used, or performing operations with elevated privileges if justified.

See also: EPERM, ENOENT, and other errno values related to access control and file system permissions.