This topic provides a general overview of regular expression notation.
for more information. A regular expression notation specifies a pattern of character strings. One or more regular expressions can be used to create a matching pattern. Certain characters (sometimes called wildcards) have special meanings. The table below describes the pattern matching scheme.
Regular expression pattern matching
| Pattern | Description |
|---|---|
| string | string with no special characters matches the values that contain the string. |
| [set] | Match a single character specified by the set of single characters within the square brackets. |
| [a-z] | Match a character in the range specified within the square brackets. |
| [^abc] | Match any single character not specified in the set of single characters within the square brackets. |
| {n} | Match exactly n times. |
| {n,} | Match at least n times. |
| {n,m} | Match at least n times, but no more than m times. |
| ^ | Match the start of the string. |
| $ | Match the end of the string. |
| . | Match any character (except Newline). |
| * | Match zero or more of preceding character. |
| + | Match one or more of preceding character. |
| ? | Match one or zero of preceding character. |
| string1|string2 | Match string1 or string2. |
| \ | Signifies an escape character. When preceding any of the characters that have special meaning, the escape character removes any special meaning from the character. For example, the backslash is useful to remove special meaning from a period in an IP address. |
| (group) | Group a character in a regular expression. If a match is found the first group can be accessed using $1. The second group can be accessed using $2 and so on. |
| \w | Match an alphanumeric character. |
| \s | Match a white-space character. |
| \t | Tab character. |
| \n | Newline character. |
| \r | Return character. |
| \f | Form feed character. |
| \v | Vertical tab character. |
| \a | Bell character. |
| \e | Escape character. |
| \Onn | Octal character, for example \O76. |
| \xnn | Hex character, for example \xff. |
| \cn | Control character, for example \c[. |
| \l | Lowercase next character. |
| \L | Lowercase until \E. |
| \u | Uppercase next character. |
| \U | Uppercase until \E. |
| \E | End modification. |
| \Q | Quote until \E. |
Examples of regular expression pattern matching
| Pattern | Examples of strings that match |
|---|---|
| ibm | ibm01, myibm, aibmbc |
| ^ibm$ | ibm |
| ^ibm0[0-4][0-9]$ | ibm000 through ibm049 |
| ibm[3-8] | ibm3, myibm4, aibm5b |
| ^ibm | ibm01, ibm |
| ibm$ | myibm, ibm, 3ibm |
| ibm... | ibm123, myibmabc, aibm09bcd |
| ibm*1 | ibm1, myibm1, aibm1abc, ibmkkkkk12 |
| ^ibm0.. | ibm001, ibm099, ibm0abcd |
| ^ibm0..$ | ibm001, ibm099 |
| 10.2.1.9 | 10.2.1.9, 10.2.139.6, 10.231.98.6 |
| ^10\.2\.1\.9$ | 10.2.1.9 |
| ^10\.2\.1\.1[0-5]$ | 10.2.1.10, 10.2.1.11, 10.2.1.12, 10.2.1.13, 10.2.1.14, 10.2.1.15 |
| ^192.\.168\..*\..*$ | (All addresses on class B subnet 192.168.0.0) |
| ^192.\.168\.10\..*$ | (All addresses on class C subnet 192.168.10.0) |