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Where can I find reference for less regex search patterns?

I want to search file with less using \d to find digits, but it does not seem to understand this wildcard. I tried to find a reference for less regex patterns, but could not find anything, not on man pages and not on the Internet.

9

less's man page says:

   /pattern
          Search forward in the file for the N-th line containing
          the pattern.  N defaults to 1.  The pattern is a regular
          expression, as recognized by the regular expression library
          supplied by your system.

so the accepted syntax may depend on your system. Off-hand, it seems to accept extended regular expressions on my Debian system, see regex(7), and Why does my regular expression work in X but not in Y?

\d is from Perl, and isn't supported by all regex engines. Use [0-9] or [[:digit:]] to match digits. (Their exact behaviour may depend on the locale.)

2

The expressions supported by less are documented in the re_format(7) manual (man 7 re_format). That manual describes both the extended regular expressions and the basic regular expressions available on your system. The less utility understands extended regular expressions.

To match a digit, you would use [0-9] or [[:digit:]] (there's a slight difference as the latter depends on the current locale). The \d pattern is a Perl-like regular expression (PCRE), not supported by less.

  • Thank you, your answer is as good as @ilkkachu `s. I'm sorry, but I'll accept his answer, it has useful links. I upvoted your answer, it will be visible, when I get enough reputation. – CodeSandwich Jul 3 '18 at 14:44
  • @CodeSandwich No worries :-) – Kusalananda Jul 3 '18 at 14:44

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