49.3 Regular expressions

The regular expressions that you can use in the search and replace dialogs and in places like the Feature attributes, the Primary index of an Item node or in checks all use standard Java regexp syntax as described in the Java documentation for the class java.util.regex.Pattern at http://download.oracle.com/javase/1.5.0/docs/api/java/util/regex/Pattern.html.

It's also worth having a look at the Wikipedia article about regular expressions.
Following is a short summary of the basics:

• A '.' stands for any one character except line breaks. With the new Java regexps you can start your regexp with the embedded flag '(?s)' to treat multi-line text like a single line so '.' will match everything.
• Character in between '[' and ']' match any one of these characters.
• A '?' says the preceding element is optional, i.e. it may appear 0 or 1 times.
• '+' means at least one of the preceding element.
• '*' means 0 or more of the preceding element.
• A group is created with '(' and ')'. A '?', '+' or '*' after the closing brace refers to the whole group. All groups in a regexp are numbered in the order of their opening brace. The first group has the number 1, 0 stands for the whole regexp. For search and replace, $n in the replacement string expands to the part of the original value matched by the n^th group. Example: To change the extension of file names starting with /tmp/ from .foo to .bar, search for (/tmp/.*)\.foo and replace with $1.bar.
• A '|' separates alternatives in a group.
• '\' quotes to suppress the special meaning of the following character or introduces special characters, e.g. '\n' for LineFeed (a line break), '\r' for CarriageReturn (not needed for QF-Test, see "Line breaks under Linux and Windows") or '\t' for Tab.

Examples:

• .* describes a sequence of arbitrary characters, which is optional.
• .+ describes a sequence of arbitrary characters, but there must be at least one character, i.e. some mandatory characters.
• [0-9] describes one arbitrary cipher.
• [0-9]+ describes a sequence of arbitrary ciphers, but there must be at least one cipher.
• [0-9]{1,3} describes a sequence of arbitrary ciphers, but there must be at least one cipher and at maximum three ciphers.
• To match any text that contains the word 'tree' use '.*tree.*'.
• To match arbitrary text possibly including line breaks: '(?s).*'
• To replace 'tree' in arbitrary text with 'node' use '(.*)tree(.*)' to search and $1node$2 to replace. In the replace dialog simply replace tree with node and disable the "Match whole string" check box to achieve the same effect.
• To search for 'name' or 'names': 'names?'
• To search for 'tree' or 'node': '(tree|node)'
• An arbitrary word consisting of letters and numbers: [0-9a-zA-Z]+
• ...

QF-Test allows you to use the context menu item »Escape text for regular expressions« on all attributes which allow regular expressions in order to escape special characters of regular expressions correctly with '\'. When it is not possible to use that functionality, for example with variables, you can use the special syntax ${quoteregexp:$(myVariable)} to excape special characaters in the variable value, see Special groups.