Is \d not supported by grep's basic expressions? [closed]

Closed. This question does not meet Stack Overflow guidelines. It is not currently accepting answers.

---

This question does not appear to be about a specific programming problem, a software algorithm, or software tools primarily used by programmers. If you believe the question would be on-topic on another Stack Exchange site, you can leave a comment to explain where the question may b开发者_如何学Goe able to be answered.

Closed 1 year ago.

The community reviewed whether to reopen this question last year and left it closed:

Original close reason(s) were not resolved

Improve this question

This does not generate any output. How come?

$ echo 'this 1 2 3' | grep '\d\+'

But these do:

$ echo 'this 1 2 3' | grep '\s\+'
this 1 2 3

$ echo 'this 1 2 3' | grep '\w\+'
this 1 2 3

---

As specified in POSIX, grep uses basic regular expressions, but \d is part of a Perl-compatible regular expression (PCRE).

If you are using GNU grep, you can use the -P option, to allow use of PCRE regular expressions. Otherwise you can use the POSIX-specified [[:digit:]] character class in place of \d.

echo 1 | grep -P '\d'
# output: 1
echo 1 | grep '[[:digit:]]'
# output: 1

---

Try this $ echo 'this 1 2 3' | grep '[0-9]\+'