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Pattern matching digits does not work in egrep?

Why can't I match the string

"1234567-1234567890"

with the given regular ex开发者_Python百科pression

\d{7}-\d{10}

with egrep from the shell like this:

egrep \d{7}-\d{10} file

?


egrep doesn't recognize \d shorthand for digit character class, so you need to use e.g. [0-9].

Moreover, while it's not absolutely necessary in this case, it's good habit to quote the regex to prevent misinterpretation by the shell. Thus, something like this should work:

egrep '[0-9]{7}-[0-9]{10}' file

See also

  • egrep mini tutorial

References

  • regular-expressions.info/Flavor comparison
    • Flavor note for GNU grep, ed, sed, egrep, awk, emacs
      • Lists the differences between grep vs egrep vs other regex flavors


For completeness:

Egrep does in fact have support for character classes. The classes are:

  • [:alnum:]
  • [:alpha:]
  • [:cntrl:]
  • [:digit:]
  • [:graph:]
  • [:lower:]
  • [:print:]
  • [:punct:]
  • [:space:]
  • [:upper:]
  • [:xdigit:]

Example (note the double brackets):

egrep '[[:digit:]]{7}-[[:digit:]]{10}' file


you can use \d if you pass grep the "perl regex" option, ex:

grep -P "\d{9}"


Use [0-9] instead of \d. egrep doesn't know \d.


try this one:

egrep '(\d{7}-\d{10})' file
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