In a complementary character set, the first character after [ is caret, ^, and it negates the set of characters in the square brackets. For example, to match any character except a vowel, we can use the following regular expression:
$ echo -e "a
b
c
d
e" | awk '/[^aeiou]/{ print }'
The output on execution of the preceding code is as follows:
b
c
d
Similarly, in the employee database (emp.dat), if we want to print information for all those employees whose email ID doesn't begin with either 'j' or 'v', that is, [^jv], we can use the following expression:
$ awk '$4 ~ /^[^jv]/{ print $4 }' emp.dat
The output on execution of the given code is as follows:
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
Some examples of complemented character classes are given as follows:
|
Named character class |
Matches |
|
[^a-z] |
Matches any character except a lowercase letter |
|
[^A-Z] |
Matches any character except an uppercase letter |
|
[^a-zA-Z] |
Matches any character except an alphabet character |
|
[^a-zA-Z0-9] |
Matches any character except an alphanumeric character |
|
[^5-9G-Lr-z] |
Matches any single character except among [56789GHIJKLrstuvwxyz] |
|
[^0-9] |
Matches any character except any digit |
|
^[^ABC] |
Matches any character at the beginning of a string except ABC |
|
^[ABC] |
Matches ABC at the beginning of a string |
|
^[^a-z]$ |
Matches any single-character except a lowercase letter |
|
^[^^] |
Matches any character except ^ at the beginning |