Extract the text between the nth occurrence of square brackets

Shell Programming and Scripting
1

Please can someone help with this?

I have a file with lines as follows:

word1 word2 word3 [11231] word4 word5 word6 [242] word7 word8
word1 word2 word3 [34534] word4 word5 word6 [34] word7 word8
word1 word2 word3 [345] word4 word5 word6 [2354] word7 word8
word1 word2 word3 [2342354123] word4 word5 word6 [23441] word7 word8

When I use the command

perl -lne 'print $1 while (/\[(.*?)\]/g)

'

I get the results as follows.

11231
242
34534
34
345
2354
2342354123
23441

How do I modify my script to get only the numbers inside the first set of square brackets, giving an output as follows?

11231
34534
345
2342354123

Also, how can I get only the numbers inside the second set of square brackets, giving an output as follows?

242
34
2354
23441

It isn't necessary to use perl, I can do with sed/awk, or anything else.

2

Using awk:

awk -F'[][]' -v n=1 '{ print $(2*n) }' file

Change n value as per your requirement (1 for 1st set, 2 for 2nd set...)

3

If you example is correct - meaning the first [123] is always field 4 and the second [123] is always field 8:

tr  -d '[:punct:]' < inputfile | awk '{print $4 > "outfile1";print $8 > "outfile2"}'

This creates two files: outfile1 with the first brackets value, outfile2 with the second brackets output value.

4

Thanks Yoda. I am getting the following error.
awk: syntax error near line 1
awk: bailing out near line 1
Any clue what that means?

---------- Post updated at 10:14 AM ---------- Previous update was at 10:13 AM ----------

Sorry Jim, the fields in square brackets are not in the same position on every line.

5

try

use var=1 - for print first square bracket values.
use var=2 - for print second square bracket values.

nawk -F "[][]" -v var="2" '{print $(var*2)}'  file
6

Use /usr/xpg4/bin/awk instead on SunOS or Solaris.

7

Thanks a lot, Yoda. It's working now.

8

Using Perl:

perl -lne 'print +(/\[(.*?)\]/g)[0]' file

Change the subscript to print the required match. Remember that array/list subscripting begins with 0.