Rules for Directory Regular Expressions

There are special considerations you must be aware of when you use regular expressions for directory names. This section describes these restrictions and provides some examples.

Restrictions for Using Regular Expressions as Directory Names

The following restrictions apply when using regular expressions as directory names:

• The directory root, the drive name, and directory separators must be expressed exclusively. That is, do not express any of these elements as a regular expression. Only folder names are expected to appear as regular expressions.

• A regular expression must not span over the directory separators. If you use a regular expression between two directory separators, it must be one whole expression.

• Escape all directory separators in a directory pattern if the separator conflicts with a regular expression special character (that is, ” * [ ] ( ) | + { } : . ^ $ ? \"). The back slash (\) is the special character used to escape other special characters in regular expressions. For Windows platforms, the directory separator is the back slash, so it must be escaped as \\.

• For the Windows Universal Naming Convention (UNC), the directory root (including the computer name and the shared root folder name) must be expressed exclusively. That is, do not express the computer name and shared root folder as a regular expression.

• Directory separators are platform dependent, for example:

  • For Windows platforms, the directory path follows this pattern:

    drive:\\regexp1\\regexp2\\regexp3 ...

    or for Windows UNC notation, the directory path follows this pattern:

    \\\\machineName\\shared_folder\\regexp1\\regexp2\\regexp3 ...

  • For UNIX platforms, including mounted directories, the directory path follows this pattern:

    /regexp1/regexp2/regexp3 ...

Regular Expression Directory Name Examples

The following are several examples of regular expression directory name usage:

• Windows:

  c:\\$\\^client\\collab\D\\ ...

  The expression \D indicates any non-digit character.

  d:\\a.b\\c.d\\e.f\\g.h\\[0-9]\\ ...

  The symbol “.” means any character

• Windows UNC notation:

  \\\\My_Machine\\public\\xyz$\\^abc

  The prefix for Windows UNC notation is \\. After escaping, it becomes \\\\.

• UNIX:

  /abc\d/def/ghi/ ...

  The expression \d means any digit character.

  /^PRE[0-9]{5}\.dat$/ ...

  This expression means to begin with PRE followed by a five-digit number and use a .dat extension. The symbol \. means to interpret the real character (a period) instead of any character. Therefore, PRE12345.dat does match, but PRE123456dat does not.