NAME

lchown — change the owner and group of a symbolic link

SYNOPSIS

#include <unistd.h>

int lchown(const char *path, uid_t owner, gid_t group);


DESCRIPTION

The lchown() function shall be equivalent to chown(), except in the case where the named file is a symbolic link. In this case, lchown() shall change the ownership of the symbolic link file itself, while chown() changes the ownership of the file or directory to which the symbolic link refers.

RETURN VALUE

Upon successful completion, lchown() shall return 0. Otherwise, it shall return -1 and set errno to indicate an error.

ERRORS

The lchown() function shall fail if:

[EACCES]

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

[EINVAL]

The owner or group ID is not a value supported by the implementation.

[ELOOP]

A loop exists in symbolic links encountered during resolution of the path argument.

[ENAMETOOLONG]

The length of a component of a pathname is longer than {NAME_MAX}.

[ENOENT]

A component of path does not name an existing file or path is an empty string.

[ENOTDIR]

A component of the path prefix names an existing file that is neither a directory nor a symbolic link to a directory, or the path argument contains at least one non-<slash> character and ends with one or more trailing <slash> characters and the last pathname component names an existing file that is neither a directory nor a symbolic link to a directory.

[EPERM]

The effective user ID does not match the owner of the file and the process does not have appropriate privileges.

[EROFS]

The file resides on a read-only file system.

The lchown() function may fail if:

[EIO]

An I/O error occurred while reading or writing to the file system.

[EINTR]

A signal was caught during execution of the function.

[ELOOP]

More than {SYMLOOP_MAX} symbolic links were encountered during resolution of the path argument.

[ENAMETOOLONG]

The length of a pathname exceeds {PATH_MAX}, or pathname resolution of a symbolic link produced an intermediate result with a length that exceeds {PATH_MAX}.

EXAMPLES

Changing the Current Owner of a File

The following example shows how to change the ownership of the symbolic link named /modules/pass1 to the user ID associated with "jones" and the group ID associated with "cnd".

The numeric value for the user ID is obtained by using the getpwnam() function. The numeric value for the group ID is obtained by using the getgrnam() function.

#include <sys/types.h>
#include <unistd.h>
#include <pwd.h>
#include <grp.h>


struct passwd *pwd;
struct group  *grp;
char          *path = "/modules/pass1";
...
pwd = getpwnam("jones");
grp = getgrnam("cnd");
lchown(path, pwd->pw_uid, grp->gr_gid);

APPLICATION USAGE

On implementations which support symbolic links as directory entries rather than files, lchown() may fail.

RATIONALE

None.

FUTURE DIRECTIONS

None.

SEE ALSO

chown, symlink

XBD <unistd.h>

CHANGE HISTORY

First released in Issue 4, Version 2.

Issue 5

Moved from X/OPEN UNIX extension to BASE.

Issue 6

The wording of the mandatory [ELOOP] error condition is updated, and a second optional [ELOOP] error condition is added.

The Open Group Base Resolution bwg2001-013 is applied, adding wording to the APPLICATION USAGE.

Issue 7

Austin Group Interpretation 1003.1-2001 #143 is applied.

The lchown() function is moved from the XSI option to the Base.

The [EOPNOTSUPP] error is removed.

The [ENOTDIR] error condition is clarified to cover the condition where the last component of a pathname exists but is not a directory or a symbolic link to a directory.

POSIX.1-2008, Technical Corrigendum 1, XSH/TC1-2008/0351 [324] is applied.