Menu
I want to extract a substring matching a pattern and save it to a file. An example string:
Apr 12 19:24:17 PC_NMG kernel: sd 11:0:0:0: [sdf] Attached SCSI removable disk
I want to extract the part between the brackets, in this case [sdf].
I tried to do something like grep -e '[$subtext]' to save the text in the brackets to a variable. Of course it doesn't work, but I am looking for a way similar to this. It would be very elegant to include a variable in a regex like this. What can I do best?
Thanks!
224
The pattern-matching algorithm uses a variety of techniques to match different kinds of expression. Data elements such as numbers, strings, booleans are matched by comparison: a pattern consisting of a single data element matches only that exact element.
Pattern matching in the shell against filenames has metacharacters defined differently from the rest of unix pattern matching prgorams. * is match any character except whitespace, ? is match one character except whitespace. so *. c is match any filename ending with the two characters .
match() function of re in Python will search the regular expression pattern and return the first occurrence. The Python RegEx Match method checks for a match only at the beginning of the string. So, if a match is found in the first line, it returns the match object.
sed is greedy, so the sed answers will miss out some of the data if there are more [] pairs in your data. Use the grep+tr solution or you can use awk
$ cat file
[sss]Apr 12 19:24:17 PC_NMG kernel: sd 11:0:0:0: [sdf] Attached SCSI removable disk [tag] blah blah
$ awk -F"[" '{for(i=2;i<=NF;i++){if($i~/\]/){sub("].*","",$i)};print $i}}' file
sss
sdf
tag
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
