AWK Access captured group from line pattern

Question

If I have an awk command  pattern           and pattern uses a capturing group  how can I access the string so captured in the block

User · Answer

I struggled a bit with coming up with a bash function that wraps Peter Tillemans' answer but here's what I came up with:

function regex { perl -n -e "/$1/ && printf \"%s\n\", "'$1' }

I found this worked better than opsb's awk-based bash function for the following regular expression argument, because I do not want the "ms" to be printed.

'([0-9]*)ms$'

User · Answer

This is something I need all the time so I created a bash function for it  It s based on glenn jackman s answer   Definition  Add this to your  bash profile etc   function regex   gawk  match  0    1    ary   print ary    2 - 0            Usage  Capture regex for each line in file    cat filename   regex        Capture 1st regex capture group for each line in file    cat filename   regex        1

User · Answer

You can use GNU awk     cat hta RewriteCond   HTTP HOST    www  mysite  net  RewriteRule      http   www mysite net  1  R 301 L     gawk  match  0      http         m    print m 1       lt  hta http   www mysite net

User · Answer

That was a stroll down memory lane     I replaced awk by perl a long time ago   Apparently the AWK regular expression engine does not capture its groups   you might consider using something like    perl -n -e  test  d     amp  amp  print  1    the -n flag causes perl to loop over every line like awk does

User · Answer

You can simulate capturing in vanilla awk too  without extensions  Its not intuitive though   step 1  use gensub to surround matches with some character that doesnt appear in your string  step 2  Use split against the character  step 3  Every other element in the splitted array is your capture group      echo  ab cb ad    awk    split gensub  a   SUBSEP   SUBSEP  g   0  cap SUBSEP   print cap 2     cap 4       ab ad

User · Answer

With gawk  you can use the match function to capture parenthesized groups   gawk  match  0  pattern  ary   print ary 1       example   echo  abcdef    gawk  match  0   b    e   a   print a 1       outputs cd    Note the specific use of gawk which implements the feature in question   For a portable alternative you can achieve similar results with match   and substr   example   echo  abcdef    awk  match  0   b  e      print substr  0  RSTART 1  RLENGTH-1      outputs cd

[regex] AWK: Access captured group from line pattern

Examples related to regex

Examples related to awk