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I'm not sure what I'm doing wrong. Given a test.log of:

123.123.123.123 321.321.321.321 GET /test1234/asdfasdfpioasdfjkhweris,9
123.123.123.123 321.321.321.321 GET /4321test/asdfasdfpioasdfjkhweris,9
123.123.123.123 321.321.321.321 GET /test123456/asdfasdfpioasdfjkhweris,9

I am trying to isolate the first two by specifying the number of characters between the / and /.

This works

cat test* | awk '{if($4 ~ /^\/[a-zA-Z0-9][a-zA-Z0-9][a-zA-Z0-9][a-zA-Z0-9][a-zA-Z0-9][a-zA-Z0-9][a-zA-Z0-9][a-zA-Z0-9]\//) print $0}'

But this does not

cat test* | awk '{if($4 ~ /^\/[a-zA-Z0-9]{8,}\//) print $0}'

What am I missing?

I've also tried:

cat test* | awk '$4 ~ /^\/[a-zA-Z0-9]{8}\// {print $0}'

which didn't work either.

UPDATE: I also tried the same commands using gawk, which is also available for me to use, and they still didn't work.

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    Is your awk implementation provided by mawk? It looks like mawk doesn't support the {m,n} syntax at all. Try using a more full featured implementation like GNU's gawk. – jw013 May 29 '15 at 3:24
  • @jw013 gawk is also on this machine. Will the same string work with gawk? – user112802 May 29 '15 at 3:27
  • It should, but why don't you just try it and see? – jw013 May 29 '15 at 3:27
  • I did, and it isn't working. I will update my main post. – user112802 May 29 '15 at 3:28
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    The two awk commands work for me (with GNU awk 4.x). (Older awks may not have supported the brace quantifiers.) - Unrelated, but BTW, you should omit the cat and let awk open the files: awk ' ... ' test*. – Janis May 29 '15 at 4:05
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cat test* | gawk --re-interval '$4 ~ /^\/[a-zA-Z0-9]{8}\// {print $0}'
# OR
cat test* | gawk --re-interval '{if( $4 ~ "^/[a-zA-Z0-9]{8}/") {print $0}}'

From GNU awk's manpage:

  • --re-interval – Enable the use of interval expressions in regular expression matching

Re also ensuring that at least on numeric digit is included: 

gawk --re-interval '$4 ~ "^/[a-zA-Z0-9]{8}/" &&
                    $4 ~ "^/[^/]{0,7}[0-9]" {print $0}'
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  • Which should of course be equivalent to the non-imperative "awk'ish" form: awk --re-interval '$4 ~ /^\/[a-zA-Z0-9]{8}\//' – Janis May 29 '15 at 4:13
  • @Janis or Peter.O Now how could I ensure there was at least one number in that 8 character string? – user112802 May 29 '15 at 4:18
  • I'd try (untested): awk --re-interval '$4 ~ /^\/[a-zA-Z0-9]{8}\// && substr($4,2,8) ~ /[0-9]/'. – Janis May 29 '15 at 4:22
  • awk --re-interval '$4 ~ /^\/[a-zA-Z0-9]{8}\// && $4 ~ /^\/.{1,7}[0-9]/' test.log appears to work. I'll try your example next. – user112802 May 29 '15 at 4:25
  • Well, that's another option. (Maybe a bit more cryptic than the substr() suggestion.) - But as you wrote it it would not match a leading digit; shouldn't that be {0,7} according to your question? – Janis May 29 '15 at 4:31
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why not try .. ?

awk -F/ 'length($2) == 8 '
  • -F/ use / as separator
  • length($2) compute length
  • default awk action print it
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