Example

This example demonstrates how you can get the ACL for a file, modify it, and then set it for the file.

#include <stdlib.h>
#include <stdio.h>
#include <sys/acl.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <fcntl.h>


int main(int argc, char *argv[]) {

	acl_t my_acl;
	char  *text_acl;
	ssize_t len;
	acl_entry_t my_entry;
	gid_t  group_id;
	acl_permset_t permset;
        int fd;

        fd = open( "my_file.txt", O_CREAT | O_RDONLY, 0666 );
        close(fd);

	/* Get the file's ACL. */
	my_acl = acl_get_file ("my_file.txt", ACL_TYPE_ACCESS);
	if (my_acl == NULL)
	{
		perror ("acl_get_file()");
		return EXIT_FAILURE;
	}

	/* Convert the ACL into text so we can see what it is. */
	text_acl = acl_to_text (my_acl, &len);
	if (text_acl == NULL)
	{
		perror ("acl_to_text()");
		return EXIT_FAILURE;
	}
	printf ("Initial ACL: %s\n", text_acl);

	/* We're done with the text version, so release it. */
	acl_free (text_acl);

	/* Add an entry for a named group to the ACL. */
	if (acl_create_entry (&my_acl, &my_entry) == -1)
	{
		perror ("acl_create_entry()");
		return EXIT_FAILURE;
	}

	if (acl_set_tag_type (my_entry, ACL_GROUP) == -1)
	{
		perror ("acl_set_tag_type");
		return EXIT_FAILURE;
	}

	group_id = 120;
	if (acl_set_qualifier (my_entry, &group_id) == -1)
	{
		perror ("acl_set_qualifier");
		return EXIT_FAILURE;
	}

	/* Modify the permissions. */
	acl_get_permset (my_entry, &permset);
	acl_clear_perms (permset);

	if (acl_add_perm (permset, ACL_READ))
	{
		perror ("acl_add_perm");
		return EXIT_FAILURE;
	}

	/* Recalculate the mask entry. */
	if (acl_calc_mask (&my_acl))
	{
		perror ("acl_calc_mask");
		return EXIT_FAILURE;
	}

	/* Make sure the ACL is valid. */
	if (acl_valid (my_acl) ==-1)
	{
		perror ("acl_valid");
		return EXIT_FAILURE;
	}

	/* Update the ACL for the file. */
	if (acl_set_file ("my_file.txt", ACL_TYPE_ACCESS, my_acl) == -1)
	{
		perror ("acl_set_file");
		return EXIT_FAILURE;
	}

	/* Free the ACL in working storage. */
	acl_free (my_acl);

	/* Verify that it all worked, by getting and printing the file's ACL. */
	my_acl = acl_get_file ("my_file.txt", ACL_TYPE_ACCESS);
	if (my_acl == NULL)
	{
		perror ("acl_get_file()");
		return EXIT_FAILURE;
	}

	text_acl = acl_to_text (my_acl, &len);
	if (text_acl == NULL)
	{
		perror ("acl_to_text()");
		return EXIT_FAILURE;
	}
	printf ("Updated ACL: %s\n", text_acl);

	/* We're done with the text version, so release it. */
	acl_free (text_acl);

	return EXIT_SUCCESS;
}