grep

Bash: extracting first or last N octets, paths, or domain from string with fixed separator


Categories: Linux

When parsing a string that is divided by a separator char, getting the first N values OR last N values is a common scenario when dealing with: IP address separated by periods, e.g. “10.11.12.13” File path separated by forward slash “/tmp/myfolder/subpath1/subpath2/subpath3” Fully qualified domain separated by periods “sub1.sub2.my.domain.com”

Bash: grep with LookBehind and LookAhead to isolate desired text


Categories: Scripting

grep has support for Perl compatible regular expressions (PCRE) by using the -P flag, and this provides a number of useful features.  In this article, I’ll show how LookBehind and LookAhead regular expression support can provide enhanced parsing abilities to your shell scripts. For example, consider an xml file “test.xml” with the contents: <root> <path>/my/data</path> … Bash: grep with LookBehind and LookAhead to isolate desired text