Expression | Matches |
abc | “abc” (the exact character sequence, but anywhere in the string) |
^abc | “abc” at the beginning of the string |
abc$ | “abc” at the end of the string |
a|b | Either “a” or “b” |
^abc|abc$ | The string “abc” at the beginning or at the end of the string |
ab{2,4}c | “a” followed by two, three or four “b”s followed by a “c” |
ab{2,}c | “a” followed by at least two “b”s followed by a “c” |
ab*c | “a” followed by any number (zero or more) of “b”s followed by a “c” |
ab+c | “a” followed by one or more b's followed by a c |
ab?c | “a” followed by an optional “b” followed by a” c”; that is, either “abc” or ”ac” |
a.c | “a” followed by any single character (not newline) followed by a” c “ |
a\.c | “a.c” exactly |
[abc] | Any one of “a”, “b” and “c” |
[Aa]bc | Either of “Abc” and “abc” |
[abc]+ | Any (nonempty) string of “a”s, “b”s and “c”s (such as “a”, “abba”, ”acbabcacaa”) |
[^abc]+ | Any (nonempty) string which does not contain any of “a”, “b”, and “c” (such as “defg”) |
\d\d | Any two decimal digits, such as 42; same as \d{2} |
/i | Makes the pattern case insensitive. For example, /bad language/i blocks any instance of bad language regardless of case. |
\w+ | A “word”: A nonempty sequence of alphanumeric characters and low lines (underscores), such as foo and 12bar8 and foo_1 |
100\s*mk | The strings “100” and “mk” optionally separated by any amount of white space (spaces, tabs, newlines) |
abc\b | “abc” when followed by a word boundary (for example, in “abc!” but not in “abcd”) |
perl\B | “perl” when not followed by a word boundary (for example, in “perlert” but not in “perl stuff”) |
\x | Tells the regular expression parser to ignore white space that is neither preceded by a backslash character nor within a character class. Use this to break up a regular expression into (slightly) more readable parts. |
/x | Used to add regular expressions within other text. If the first character in a pattern is forward slash '/', the '/' is treated as the delimiter. The pattern must contain a second '/'. The pattern between ‘/’ will be taken as a regular expressions, and anything after the second ‘/’ will be parsed as a list of regular expression options ('i', 'x', etc). An error occurs if the second '/' is missing. In regular expressions, the leading and trailing space is treated as part of the regular expression. |