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@(#)chown.2 8.4 (Berkeley) 4/19/94
$FreeBSD: head/lib/libc/sys/chown.2 178245 2008-04-16 13:03:12Z kib $
.Dd April 10, 2008 .Dt CHOWN 2 .Os .Sh NAME .Nm chown , .Nm fchown , .Nm lchown , .Nm fchownat .Nd change owner and group of a file .Sh LIBRARY .Lb libc .Sh SYNOPSIS n unistd.h .Ft int .Fn chown "const char *path" "uid_t owner" "gid_t group" .Ft int .Fn fchown "int fd" "uid_t owner" "gid_t group" .Ft int .Fn lchown "const char *path" "uid_t owner" "gid_t group" .Ft int .Fn fchownat "int fd" "const char *path" "uid_t owner" "gid_t group" "int flag" .Sh DESCRIPTION The owner ID and group ID of the file named by .Fa path or referenced by .Fa fd is changed as specified by the arguments .Fa owner and .Fa group . The owner of a file may change the .Fa group to a group of which he or she is a member, but the change .Fa owner capability is restricted to the super-user.
p The .Fn chown system call clears the set-user-id and set-group-id bits on the file to prevent accidental or mischievous creation of set-user-id and set-group-id programs if not executed by the super-user. The .Fn chown system call follows symbolic links to operate on the target of the link rather than the link itself.
p The .Fn fchown system call is particularly useful when used in conjunction with the file locking primitives (see .Xr flock 2 ) .
p The .Fn lchown system call is similar to .Fn chown but does not follow symbolic links.
p The .Fn fchownat system call is equivalent to the .Fn chown and .Fn lchown except in the case where .Fa path specifies a relative path. In this case the file to be changed is determined relative to the directory associated with the file descriptor .Fa fd instead of the current working directory.
p Values for .Fa flag are constructed by a bitwise-inclusive OR of flags from the following list, defined in n fcntl.h : l -tag -width indent t Dv AT_SYMLINK_NOFOLLOW If .Fa path names a symbolic link, ownership of the symbolic link is changed. .El
p If .Fn fchownat is passed the special value .Dv AT_FDCWD in the .Fa fd parameter, the current working directory is used and the behavior is identical to a call to .Fn chown or .Fn lchown respectively, depending on whether or not the .Dv AT_SYMLINK_NOFOLLOW bit is set in the .Fa flag argument.
p One of the owner or group id's may be left unchanged by specifying it as -1. .Sh RETURN VALUES .Rv -std .Sh ERRORS The .Fn chown and .Fn lchown will fail and the file will be unchanged if: l -tag -width Er t Bq Er ENOTDIR A component of the path prefix is not a directory. t Bq Er ENAMETOOLONG A component of a pathname exceeded 255 characters, or an entire path name exceeded 1023 characters. t Bq Er ENOENT The named file does not exist. t Bq Er EACCES Search permission is denied for a component of the path prefix. t Bq Er ELOOP Too many symbolic links were encountered in translating the pathname. t Bq Er EPERM The operation would change the ownership, but the effective user ID is not the super-user. t Bq Er EPERM The named file has its immutable or append-only flag set, see the .Xr chflags 2 manual page for more information. t Bq Er EROFS The named file resides on a read-only file system. t Bq Er EFAULT The .Fa path argument points outside the process's allocated address space. t Bq Er EIO An I/O error occurred while reading from or writing to the file system. .El
p The .Fn fchown system call will fail if: l -tag -width Er t Bq Er EBADF The .Fa fd argument does not refer to a valid descriptor. t Bq Er EINVAL The .Fa fd argument refers to a socket, not a file. t Bq Er EPERM The effective user ID is not the super-user. t Bq Er EROFS The named file resides on a read-only file system. t Bq Er EIO An I/O error occurred while reading from or writing to the file system. .El
p In addition to the errors specified for .Fn chown and .Fn lchown , the .Fn fchownat system call may fail if: l -tag -width Er t Bq Er EBADF The .Fa path argument does not specify an absolute path and the .Fa fd argument is neither .Dv AT_FDCWD nor a valid file descriptor open for searching. t Bq Er EINVAL The value of the .Fa flag argument is not valid. t Bq Er ENOTDIR The .Fa path argument is not an absolute path and .Fa fd is neither .Dv AT_FDCWD nor a file descriptor associated with a directory. .El .Sh SEE ALSO .Xr chgrp 1 , .Xr chflags 2 , .Xr chmod 2 , .Xr flock 2 , .Xr chown 8 .Sh STANDARDS The .Fn chown system call is expected to conform to .St -p1003.1-90 . The .Fn fchownat system call follows The Open Group Extended API Set 2 specification. .Sh HISTORY The .Fn chown function appeared in .At v7 . The .Fn fchown system call appeared in x 4.2 .
p The .Fn chown system call was changed to follow symbolic links in x 4.4 . The .Fn lchown system call was added in .Fx 3.0 to compensate for the loss of functionality.
p The .Fn fchownat system call appeared in .Fx 8.0 .