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• here are some good ones:
  • a good general one: https://www.regular-expressions.info/
  • Ryan's tutorials on Regular Expressions: http://ryanstutorials.net/regular-expressions-tutorial/
  • RegexOne: http://regexone.com
• and a perl regex tutorial: http://perldoc.perl.org/perlretut.html
  • perl regular expressions are the "gold standard" used in most other languages

perl pattern matching

If grep pattern matching isn't behaving the way I expect, I turn to perl. While Perl, like awk, is a fully functional programming language, Here's how to invoke regex pattern matching from a command line using perl:

perl -n -e 'print $_ if $_=~/<pattern>/'

sed pattern substitution

The sed (string editor) command can be used to edit text using pattern substitution.

sed 's/<search pattern>/<replacement>/'

While sed is very powerful, the regex syntax for its more advanced features is quite different from "standard" grep or perl regular expressions. As a result, I tend to use it only for very simple substitutions, usually as a component of a multi-pipe expression.

perl pattern substitution

If I have a more complicated pattern, or if sed pattern substitution is not working as I expect (which happens frequently!), I again turn to perl. Here's how to invoke perl pattern substitution from a command line:

perl -p -e '~s/<search pattern>/<replacement>/'

Parentheses ( ) around one or more text sections in the <search pattern> will cause matching text to be captured in built-in perl variables $1, $2, etc., following the order of the parenthesized text. The capture variables can then be used in the <replacement>.

Field delimiter summary

Be aware of the default field delimiter for the various bash utilities, and how to change them:

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Examples:

ls -l ~/.bash_history

ls -l /usr/bin/ls

ls -l -d ~/local (-d says to list directory information, not directory contents)

Copying files between TACC and your laptop

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Copying_files_to_from_TACC Copying_files_to_from_TACC

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