Regular Expressions
Use regular expressions
/regexp/
awk '/li/ { print $2 }' mail-list
exp ~ /regexp/
awk '$1 ~ /^J/' inventory-shipped
exp !~ /regexp/
awk '$1 !~ /^J/' inventory-shipped
echo aaaabcd | awk '{ sub(/a+/, "<A>"); print }'
Dynamic regexps
ls -l | awk 'BEGIN { digits_regexp = "[[:digit:]]+" } $5 ~ digits_regexp { print }'
ls -l | awk 'BEGIN { digits_regexp = "[[:alpha:]]+" } $4 ~ digits_regexp { print }'
POSIX character classes
Class |
Description |
|---|---|
[:alnum:] |
Alphanumeric characters |
[:alpha:] |
Alphabetic characters |
[:blank:] |
Space and TAB characters |
[:cntrl:] |
Control characters |
[:digit:] |
Numeric characters |
[:graph:] |
Characters that are both printable and visible 1 |
[:lower:] |
Lowercase alphabetic characters |
[:print:] |
Printable characters 2 |
[:punct:] |
Punctuation characters 3 |
[:space:] |
Space characters 4 |
[:upper:] |
Uppercase alphabetic characters |
[:xdigit:] |
Characters that are hexadecimal digits |
Ignore case
IGNORECASE = [0,1]
echo -e "ab\ncd" | awk 'BEGIN { IGNORECASE = 1 } /A/ { print }'