SymLink.h

Classes

SymLink -- Get information about, and manipulate symbolic links (full description)

class SymLink: public File

Interface

Public Members
SymLink()
SymLink (const Path& name)
SymLink (const String& name)
SymLink (const File& name)
SymLink (const SymLink& that)
~SymLink()
SymLink& operator= (const SymLink& that)
void create (const Path& target, Bool overwrite = True)
void create (const String& target, Bool overwrite = True)
void copy (const Path& target, Bool overwrite = True) const
void copy (const String& target, Bool overwrite = True) const
void move (const Path& target, Bool overwrite = True)
void move (const String& target, Bool overwrite = True)
void remove()
Path readSymLink() const
Path followSymLink() const
Private Members
void checkPath() const
String getSymLink() const

Description

Review Status

Reviewed By:
UNKNOWN
Date Reviewed:
before2004/08/25

Prerequisite

Etymology

The class SymLink handles SYMbolic LINKs in the file system.

Synopsis

SymLink provides functions to manipulate and to get information about symbolic links. The functions for getting information (like ownership, dates) about symbolic links are inherited from the File class.
The class SymLink itself provides functions to create, remove, copy, and move symbolic links. There is a function readSymLink which reads a link and then returns a path and there is a function followSymLink which reads a link recursively. If the link eventually refers to itself (a loop), an exception will be thrown.

Example

    SymLink symLink1("isLink");
    SymLink symLink2("isLink2");
    SymLink symLinkA("A");
    SymLink symLinkB("B");

    symLink1.create("~", True);    // Create a symbolic link to the home
                                   // directory. When it exists it will be
                                   // overwritten.
    symLink2.create("isLink", False); // Create a symbolic link to 
                                      // isLink. When it exists it will not
                                      // be overwritten.
    symLinkA.create(Path("B"));    // Create a recursive link
    symLinkB.create(Path("A"));    // Create a recursive link

    cout << symLink1.readSymLink() << endl;  // The homedirectory is printed
    cout << symLink2.readSymLink() << endl;  // isLink is printed
    cout << symLink2.followSymLink() << endl;// The homedirectory is printed
    cout << symLinkA.readSymLink() << endl;  // B is printed
    cout << symLinkA.followSymLink() << endl;// An exception is thrown (loop)

Motivation

Provide functions for manipulating and getting information about symbolic links.

Member Description

SymLink()

The default constructor creates a SymLink with path ".".

SymLink (const Path& name)
SymLink (const String& name)
SymLink (const File& name)

Create a SymLink with the given path. An exception is thrown if the path exist and is no symbolic link or if it does not exist, but cannot be created.

SymLink (const SymLink& that)

Copy constructor (copy semantics).

~SymLink()

SymLink& operator= (const SymLink& that)

Assignment (copy semantics).

void create (const Path& target, Bool overwrite = True)
void create (const String& target, Bool overwrite = True)

Make a symbolic link to a file given by target. An exception will be thrown if:
-target already exists and is no symlink
-or target already exists and overwrite==False

void copy (const Path& target, Bool overwrite = True) const
void copy (const String& target, Bool overwrite = True) const

Copy the symlink to the target path using the system command cp. The target path can be a directory or a file (as in cp). An exception is thrown if:
- the target directory is not writable
- or the target file already exists and overwrite==False
- or the target file already exists and is not writable

void move (const Path& target, Bool overwrite = True)
void move (const String& target, Bool overwrite = True)

Move the symlink to the target path using the system command mv. The target path can be a directory or a file (as in mv). An exception is thrown if:
- the target directory is not writable
- or the target file already exists and overwrite==False
- or the target file already exists and is not writable

void remove()

Remove a symbolic link.

Path readSymLink() const

Read value of a symbolic link and return it as a Path. If the symlink does not exist, an exception will be thrown. When the symlink points to a file with a relative name, the resulting file name gets prepended by the dirname of the symlink, which is similar to the way a shell handles symlinks. E.g. 

  ls > subdir/a
  ln -s a subdir/b
  more subdir/b
The more command shows the results of subdir/a.

Path followSymLink() const

As readSymLink, but the entire symlink chain is followed when the symlinks points to other symlinks. An exception is thrown if this results in a loop (that is, if more than 25 links are encountered).

void checkPath() const

Check if the path of the file is valid. Also resolve possible symlinks.

String getSymLink() const

Get the value of the symlink.