How to extract a specific text from gz file?

I need to extract the 5 to 11 characters from my fastq.gz data this data is just too large for running in R. So I was wondering if I can do it directly in Linux command line? The fastq file looks like this:

@NB501399:67:HFKTCBGX5:1:11101:13202:1044 1:N:0:CTTGTA
GAGGTNACGGAGTGGGTGTGTGCAGGGCCTGGTGGGAATGGGGAGACCCGTGGACAGAGCTTGTTAGAGTGTCCTAGAGCCAGGGGGAACTCCAGGCAGGGCAAATTGGGCCCTGGATGTTGAGAAGCTGGGTAACAAGTACTGAGAGAAC
+
    AAAAA#EEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEAEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEAAAEEEEEEEEEEEEEEEEAEEEEEEEEEEEEEEAEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEAE6

@NB501399:67:HFKTCBGX5:1:11101:1109:1044 1:N:0:CTTGTA
TAGGCNACCTGGTGGTCCCCCGCTCCCGGGAGGTCACCATATTGATGCCGAACTTAGTGCGGACACCCGATCGGCATAGCGCACTACAGCCCAGAACTCCTGGACTCAAGCGATCCTCCAGCCTCAGCCTCCCGAGTAGCTGGGACTACAG
+

And I only want to extract the 5 to 11 character which located in sequence part (for the first one is TNACGG, for the second is CNACCT) and makes it a new txt file. Can I do that?

Solution

Another using zgrep and positive lookbehind:

$ zgrep -oP "(?<=^[ACTGN]{4})[ACTGN]{6}" foo.gz
TNACGG
CNACCT

Explained:

zgrep : man zgrep: search possibly compressed files for a regular expression
-o Print only the matched (non-empty) parts of a matching line
-P Interpret the pattern as a Perl-compatible regular expression (PCRE).
(?<=^[ACTGN]{4}) positive lookbehind
[ACTGN]{6} match 6 named characters that are preceeded by above
foo.gz my test file