chown(2)

NAME

chown, fchown, lchown − change owner and group of a file

SYNOPSIS

#include <sys/types.h>

int chown (path, owner, group)
char ∗path;
uid_t owner;
gid_t group;

SYNOPSIS (4.2BSD)

#include <sys/types.h>

int lchown (path, owner, group)
char ∗path;
uid_t owner;
gid_t group; #include <sys/types.h>

int fchown (fildes, owner, group)
int fildes;
uid_t owner;
gid_t group;

DESCRIPTION

The owner ID and group ID of the file specified by path or referenced by the descriptor fildes are set to owner and group respectively. If owner or group is specified as −1, the corresponding ID of the file is not changed.

If the user is super-user, the privilege ID of the specified file is set to the numeric value contained in group; otherwise, the privilege ID of the specified file is set to the security label of the file’s current privilege ID and the group of the privilege referred to by group. (B1 only)

The function lchown sets the owner ID and group ID of the named file just as chown does, except in the case where the named file is a symbolic link. In this case, lchown changes the ownership of the symbolic link file itself, while chown changes the ownership of the file or directory to which the symbolic link refers.

The operating system has a configuration option {_POSIX_CHOWN_RESTRICTED}, to restrict ownership changes. When this option is in effect, a process with effective user ID these functions. equal to the file owner is prevented from changing the owner ID of the file, and may change the group of the file only to a group to which the effective user ID belongs. Only a process with the effective user ID of the super-user can arbitrarily change owner IDs whether this option is in effect or not.

Only super-user can change the file’s privilege ID to or from a privilege ID not defined on the system.

A file’s security label cannot be changed if the file is being held open by another process and the user’s real user ID is not root (character devices are exempted). All file reclassifications by chown are audited.

If chown, lchown, or fchown is invoked by other than the super-user, the set-user-ID and set-group-ID bits of the file mode, S_ISUID and S_ISGID respectively, will be cleared [see chmod(2)].

Upon successful completion, chown, lchown, and fchown mark for update the st_ctime field of the file.

chown and lchown will fail and the owner and group of the named file will remain unchanged if one or more of the following are true:

[EACCES] Search permission is denied on a component of the path prefix.

[EFAULT] Path points outside the allocated address space of the process.

[EINVAL] The path argument does not refer to a file.

[ENAMETOOLONG] The path argument exceeds {PATH_MAX} in length, or a pathname component is longer than {NAME_MAX} (see pathconf(2)).

[ENOTDIR] A component of the path prefix is not a directory.

[ENOENT] The named file does not exist, or the path argument points to an empty string.

[EPERM] The effective user ID is not super-user, the POSIX_CHOWN_RESTRICTED option is enabled, and an attempt to change ownership was attempted, or, the effective user ID is not a member of group. If the POSIX_CHOWN_RESTRICTED option is disabled, EPERM will be returned if the effective user ID is not super-user and the does not match the owner of the file.

[EPERM] The user’s current security label is not identical to the file’s security label and the effective user ID is not super-user.

[EPERM] The named file is being held open by another process.

[EPERM] The file’s privilege ID cannot be changed because the new group is not defined at the file’s current security level and the user is not super-user. (B1 only)

[EROFS] The named file resides on a read-only file system.

fchown will fail if:

[EBADF] fildes does not refer to a valid descriptor.

[EINVAL] fildes refers to a socket, not a file.

[EPERM] The effective user ID does not match the owner of the file and the effective user ID is not super-user, or the user’s current security label is not identical to the file’s security label and the user’s effective user ID is not super-user.

[EROFS] The named file resides on a read-only file system.

RETURN VALUE

Upon successful completion, a value of 0 is returned. Otherwise, a value of −1 is returned and errno is set to indicate the error.

NOTE

The chown function is defined in the 88open Binary and Object Compatibility Standards (BCS/OCS) for use in BCS/OCS compliant applications. The fchown function is defined in the 88open BCS/OCS Networking Supplements (BCSNS/OCSNS) for use in BCS/OCS compliant networking applications. OCS/OCSNS-defined functions may be accessed by passing OCS options to cc(1) and ld(1).

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