Menu
I am aware of nano's search and replace functionality, but is it capable of using regular expressions for matching and substitution (particularly substitutions that use a part of the match)? If so, can you provide some examples of the syntax used (both for matching and replacing)?
I cut my teeth on Perl-style regular expressions, but I've found that text editors will sometimes come up with their own syntax.
593
Substitutions are language elements that are recognized only within replacement patterns. They use a regular expression pattern to define all or part of the text that is to replace matched text in the input string. The replacement pattern can consist of one or more substitutions along with literal characters.
To match a character having special meaning in regex, you need to use a escape sequence prefix with a backslash ( \ ). E.g., \. matches "." ; regex \+ matches "+" ; and regex \( matches "(" . You also need to use regex \\ to match "\" (back-slash).
Regular expression matching can be simple and fast, using finite automata-based techniques that have been known for decades. In contrast, Perl, PCRE, Python, Ruby, Java, and many other languages have regular expression implementations based on recursive backtracking that are simple but can be excruciatingly slow.
Being more specific with your regular expressions, even if they become much longer, can make a world of difference in performance. The fewer characters you scan to determine the match, the faster your regexes will be.
My version of nano has an option to swtich to regex search with the meta character + R. In cygwin on Windows, the meta-key is alt, so I hit ctrl+\ to get into search-and-replace mode, and then alt+r to swtich to regex search.
126
You need to add, or un-comment, the following entry in your global nanorc file (on my machine, it was /etc/nanorc):
set regexp
Then fire up a new terminal and press CTRL + / and do your replacements which should now be regex-aware.
Search for conf->(\S+):
Replace with \1_conf
Press a to replace all occurrences:
End result:
25
The regular expression format / notation for nano use "Extended Regular Expression", i.e. POSIX Extended Regular Expression, which is used by egrep and sed -r, this include metacharacters ., [ and ], ^, $, (, ), \1 to \9, *, { and }, ?, +, |, and character classes like [:alnum:], [:alpha:], [:cntrl:], [:digit:], [:graph:], [:lower:], [:print:], [:punct:], [:space:], [:upper:], and [:xdigit:].
For more complete documentation you can see manual page, man 7 regex in Linux or man 7 re_format in OS X. This page may give you same information as well: https://en.wikipedia.org/wiki/Regular_expression#POSIX_basic_and_extended
Unfortunately in nano there seems to be no way to match anything that span across multiple lines.
14
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
