Posted about 2 years ago. Visible to the public. Repeats.
grep: regex
You can use three different versions of the regular expression syntax in grep:
- basic:
-G - extended:
-E - perl:
-P
Difference between basic and extended:
CopyIn basic regular expressions the meta-characters '?', '+', '{', '|', '(', and ')' lose their special meaning; instead use the backslashed versions '\?', '\+', '\{', '\|', '\(', and '\)'.
Difference between extended (POSIX) and perl (PCRE): E.g. \d is not supported in POSIX.
This grep command searches for the same pattern in different regular expression versions.
Copygrep -G "[0-9]\{4\}ms" production.log grep -E "[0-9]{4}ms" production.log grep -P "\d{4}ms" production.log
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