acl_get_fd - Linux

Overview

acl_get_fd retrieves the access control list (ACL) associated with the file descriptor fd. ACLs are used to specify the access permissions for files and directories.

Syntax

#include <sys/acl.h>

int acl_get_fd(int fd, int type);

• fd: File descriptor of the file or directory whose ACL is to be retrieved.
• type: Specifies the type of ACL to be retrieved. It can be any one of the following:
  • ACL_TYPE_ACCESS: Retrieve the access ACL (default).
  • ACL_TYPE_DEFAULT: Retrieve the default ACL.

Options/Flags

None.

Examples

Get the access ACL of a file

#include <sys/acl.h>

int main() {
    int fd = open("myfile", O_RDONLY);
    if (fd == -1) {
        perror("open");
        exit(EXIT_FAILURE);
    }

    acl_t acl = acl_get_fd(fd, ACL_TYPE_ACCESS);
    if (acl == NULL) {
        perror("acl_get_fd");
        exit(EXIT_FAILURE);
    }

    // Use the ACL here

    acl_free(acl);
    close(fd);
    return 0;
}

Get the default ACL of a directory

#include <sys/acl.h>

int main() {
    int fd = open("mydirectory", O_RDONLY);
    if (fd == -1) {
        perror("open");
        exit(EXIT_FAILURE);
    }

    acl_t acl = acl_get_fd(fd, ACL_TYPE_DEFAULT);
    if (acl == NULL) {
        perror("acl_get_fd");
        exit(EXIT_FAILURE);
    }

    // Use the ACL here

    acl_free(acl);
    close(fd);
    return 0;
}

Common Issues

• Permission denied: Ensure that the user has sufficient permissions to retrieve the ACL.
• Invalid file descriptor: Verify that the file descriptor is valid and refers to an open file or directory.

Integration

acl_get_fd can be combined with other ACL-related commands, such as acl_set_fd and acl_get_file, to manage ACLs for files and directories.

Related Commands

• acl_set_fd: Set the ACL for a file descriptor.
• acl_get_file: Retrieve the ACL for a file or directory.