markp-fuso
2020-11-30 00:52:58
A few small changes to OPs current code:
- as mentioned in the comments,
^and$represent the beginning and ending of the input; remove these from the regex - while
grepcan use the resulting regex it will be necessary to tellgrepto run in-Extended regex mode - we can use
grep's-ooption to limit output to just the portion that matches the regex
Sample input data:
$ cat jdk.dat
openjdk 11.0.9.1 2020-11-04
OpenJDK Runtime Environment (build 11.0.9.1+1-Ubuntu-0ubuntu1.18.04)
OpenJDK 64-Bit Server VM (build 11.0.9.1+1-Ubuntu-0ubuntu1.18.04, mixed mode,sharing)
One grep solution using OP's modified regex:
$ grep -oE '[0-9]{1,2}\.[0-9]{1,2}\.[0-9]{1,2}\.[0-9]{1,2}' jdk.dat
11.0.9.1
11.0.9.1
11.0.9.1
Same thing but with the regex stored in OPs variable:
$ VERSION_EXTRACTION_REGEX='[0-9]{1,2}\.[0-9]{1,2}\.[0-9]{1,2}\.[0-9]{1,2}'
$ grep -oE "${VERSION_EXTRACTION_REGEX}" jdk.dat
11.0.9.1
11.0.9.1
11.0.9.1
NOTE: I'll leave it up to the user to decide which value to use, eg, head -n 1 to work with just the first input line (openjdk 11.0.9.1 2020-11-04)
Uh, I think you mean the opposite; Awk can handle (roughly) ERE syntax, while plain
grepcan't, and requires-Eto enable support.more like ... arg ... was jumping between a couple different answers; have updated to replace the
awkreferences withgrep; and thanks for the edit (perhaps I should step away from the keyboard for a while ...)