Help on Searching

If you aren't versed in Unix regular expressions, then here's some information that should help.

To search for a particular word or phrase, just enter the text itself. For example, to search for the phrase "Poqet Computer", just enter "Poqet Computer" (without the quotes) in the text box.

To search for two words or phrases together on the same line, seperate the two words with the characters ".*". For example to search lines that contain the phrase "Poqet Computer" followed by "Fujitsu", enter "Poqet Computer.*Fujitsu" in the text box.

To search for more than one word at a time, seperate the words with a "vertical bar" ("|"). For example to search for lines that contain the word "Poqet" or the word "Fujtisu," enter "Poqet|Fujitsu" in the text box.

The Gory Details

• A regular expression matches a string if any of the alternatives of the regular expression match. Alternatives are separated by the | character (usually called a vertical bar), and are always evaluated left-to-right, stopping on the first complete match.
• An alternative matches if every item in the alternative matches in the order the items occur.
• An item consists of either an assertion or a quantified atom. Assertions are:

  ^  Matches the beginning of the line
  $  Matches the end of the line
  \b Matches on word boundary (between \w and \W)
  \B Matches on non-word boundary

• A quantified atom consists of one of the atoms listed below followed by a quantifier, which indicates how many times the atom must or may not occur. If there is no quantifier, the atom must occur exactly once. Quantifiers are:

  {n,m} Must occur at least n times but no more than m times
  {n,}  Must occur at least n times
  {n}   Must match exactly n times
  *     0 or more times (same as {0,})
  +     1 or more times (same as {1,})
  ?     0 or 1 times (same as {0,1})

• A regular expression in parentheses matches whatever the regular expression matches.
• A . matches any character
• A list of characters in square brackets matches on of a class of characters. A caret at the front of the list negates the class. Character ranges may be indicated using the a-z notation. You may also use any of \d, \w, \s, \n, \r, \t, \f, or \nnn as listed below. A \b means a backspace in a character class. You may also use a backslash to protect a hyphen that would otherwise be interpreted as a range delimiter.
• A backslashed letter matches a special character or character class:

  \n Newline
  \r Carriage return
  \t Tab
  \f Formfeed
  \d A digit, same as [0-9]
  \D A non-digit
  \w A word character (alphanumeric), same as [0-9a-z_A-Z]
  \W A non-word character
  \s A whitespace character, same as [ \f\n\r\f]
  \S A non-whitespace character

• A backslashed single digit number matches whatever the corresponding parentheses actually matched (except that \0 matches a null character). This is called a backreference to a substring. A backslashed multi-digit number such as \10 will be considered a backreference if the pattern contains at least that many substrings prior to it, and the number does not start with a 0.
• A backslashed 2 or 3 digit octal number such as \033 matches the character with the specified value, unless it would be interpreted as a backreference.
• A backslashed x followed by two hexadecimal digits, such as \x7f, matches the character having that hexadecimal value.
• A backslashed c followed by a single character, such as \cD, matches the corresponding control character.
• Any other backslashed character matches that character.
• Any character not mentioned above matches itself.