v_symlink (BPX1VSY, BPX4VSY) — Create a symbolic link

Function

The v_symlink service creates a symbolic link to a path name or external name. A file whose name is specified in the Link_name parameter, of type "symbolic link", is created within the directory that is represented by Directory_vnode_token. The contents of the symbolic link file is the path name or external name that is specified in Pathname.

Requirements

Operation	Environment
Authorization:	Supervisor state or problem state, any PSW key
Dispatchable unit mode:	Task
Cross memory mode:	PASN = HASN
AMODE (BPX1VSY):	31-bit
AMODE (BPX4VSY):	64-bit
ASC mode:	Primary mode
Interrupt status:	Enabled for interrupts
Locks:	Unlocked
Control parameters:	All parameters must be addressable by the caller and in the primary address space.

Format

CALL BPX1VSY,(Directory_vnode_token,
              OSS,
              Link_name_length,
              Link_name,
              Pathname_length,
              Pathname,
              Attr_length,
              Attr,
              Return_value,
              Return_code,
              Reason_code)

AMODE 64 callers use BPX4VSY with the same parameters.

Parameters

Directory_vnode_token

Supplied parameter

Type:: Token
Length:: 8 bytes

The name of an 8-byte area that contains a vnode token that represents the directory in which the v_symlink service creates the new symbolic link file that is named in the Link_name parameter.

OSS

Supplied and returned parameter

Type:: Structure
Length:: OSS#LENGTH (from the BPXYOSS macro)

The name of an area that contains operating-system-specific parameters. This area is mapped by the BPXYOSS macro (see BPXYOSS — Map operating system specific information).

Link_name_length

Supplied parameter

Type:: Integer
Length:: Fullword

The name of a fullword that contains the length of Link_name. The Link_name can be up to 255 bytes long.

Link_name

Supplied parameter

Type:: Character string
Length:: Specified by Link_name_length parameter

The name of a field that contains the symbolic link that is being created. It must not contain null characters (X'00').

Pathname_length

Supplied parameter

Type:: Integer
Length:: Fullword

The name of a fullword that contains the length of Pathname. The Pathname can be up to 1023 bytes long. If the Pathname is not an external name (AttrExtLink = 0), each component of the name (between delimiters) can be up to 255 bytes long.

Pathname

Supplied parameter

Type:: Character string
Length:: Specified by the Pathname_length parameter

The name of a field that contains the path name or external name for which you are creating a symbolic link.

A path name can begin with or without a slash.

If the path name begins with a slash, it is an absolute path name, the slash refers to the root directory, and the search for the file starts at the root directory.
If the path name does not begin with a slash, it is a relative path name, and the search for the file starts at the parent directory of the symbolic link file.

A path name must not contain null characters (X'00').

An external name is the name of an object that is outside the hierarchical file system. There are no restrictions on the characters that may be used in an external name.

Attr_length

Supplied parameter

Type:: Integer
Length:: Fullword

The name of a fullword that contains the length of Attr. To determine the value of Attr_length, use the ATTR structure (see BPXYATTR — Map file attributes for v_ system calls).

Attr

Supplied parameter

Type:: Structure
Length:: Specified by the Attr_length parameter

The name of an area, of length Attr_length, that is to be used by the v_symlink service to set the attributes of the file that is to be created. This area is mapped by the ATTR structure (see BPXYATTR — Map file attributes for v_ system calls).

Return_value

Returned parameter

Type:: Integer
Length:: Fullword

The name of a fullword in which the v_symlink service returns 0 if the request is successful, or -1 if it is not successful.

Return_code

Returned parameter

Type:: Integer
Length:: Fullword

The name of a fullword in which the v_symlink service stores the return code. The v_symlink service returns Return_code only if Return_value is -1. See z/OS UNIX System Services Messages and Codes for a complete list of possible return code values. The v_symlink service can return one of the following values in the Return_code parameter:

Return_code	Explanation
EACCES	The calling process does not have permission to write in the directory specified.
EEXIST	Link_name already exists.
EFBIG	The file size limit for the process is set to zero, prohibiting the creation of symbolic links.
EINVAL	Parameter error; for example, a supplied area was too small. The following reason codes can accompany the return code: JRSmallAttr, JRInvalidAttr, JRNoName, JRInvalidSymLinkLen, JRNULLInPath, JRInvalidSymLinkComp, JRVTokenFreed, JRWrongPID, JRStaleVnodeTok, JRInvalidVnodeTok, JRInvalidOSS.
ENAMETOOLONG	Link_name is longer than 255 characters.
ENOTDIR	The supplied token did not represent a directory.
EPERM	The operation is not permitted. The caller of the service is not registered as a server.
EROFS	Directory_vnode_token specifies a directory on a read-only file system.

Reason_code

Returned parameter

Type:: Integer
Length:: Fullword

The name of a fullword in which the v_symlink service stores the reason code. The v_symlink service returns a Reason_code only if Return_value is -1. Reason_code further qualifies the Return_code value. See z/OS UNIX System Services Messages and Codes for the reason codes.

Usage notes

The following Attr fields are provided by the caller:
AttrID

Contains Attr#ID (from the ATTR structure)

AttrLen

Specifies the length of the ATTR structure.

AttrExtLink

Specifies whether the Pathname is an external name (1) or a path name in a hierarchical file system (0).

AttrMode

Specifies directory mode permission bits. See Mapping macros in z/OS UNIX System Services Programming: Assembler Callable Services Referencefor the mapping of this field.

Other fields in the ATTR should be set to zeros.
Like a hard link (described in v_link (BPX1VLN, BPX4VLN) — Create a link to a file), a symbolic link allows a file to have more than one name. The presence of a hard link guarantees the existence of a file, even after the original name has been removed. A symbolic link, however, provides no such assurance; in fact, the file identified by Pathname need not exist when the symbolic link is created. In addition, a symbolic link can cross file system boundaries, and can refer to objects that are outside a hierarchical file system.
When a component of a path name refers to a symbolic link (but not an external symbolic link) rather than to a directory, the path name that is contained in the symbolic link is resolved. When the VFS callable services API, v_rpn, or other z/OS UNIX callable services are being used, a symbolic link in a path name parameter is resolved as follows:
- If the path name in the symbolic link begins with / (slash), the symbolic link path name is resolved relative to the process root directory.
- If the path name in the symbolic link does not begin with /, the symbolic link path name is resolved relative to the directory that contains the symbolic link.
- If the symbolic link is not the last component of the original path name, remaining components of the original path name are resolved from there.
- When a symbolic link is the last component of a path name, it may or may not be resolved. Resolution depends on the function that is using the path name. For example, a rename request does not have a symbolic link resolved when it appears as the final component of either the new or old path name. However, an open request does have a symbolic link resolved when it appears as the last component.
- When a slash is the last component of a path name, and it is preceded by a symbolic link, the symbolic link is always resolved.
- The mode of a symbolic link is ignored during the lookup process. Any files and directories to which a symbolic link refers are checked for access permission.
The external name that is contained in an external symbolic link is not resolved. Link_name cannot be used as a directory component of a path name.
If the file size limit for the process is set to zero, symbolic link creation is prohibited and fails with EFBIG.
The value that is set by umask() for the process does not affect the setting of the mode permission bits.

Related services

Characteristics and restrictions

A process must be registered as a server before the v_symlink service is permitted; see v_reg (BPX1VRG, BPX4VRG) — Register a process as a server.

Examples

For an example using this callable service, see BPX1VSY, BPX4VSY (v_symlink).