#Linux tools for examining #sequencing data:
```
zcat sequences.fastq.gz | \
awk 'NR % 4 == 2 { print substr($0, 0, 10) }' |\
sort | uniq -c | sort -nr > index_list
```
Generates a list of the first 10 bases in sequences.fastq.gz, sorted by frequency. Handy if you need to check that the indexes you thought you used are in fact the ones that were used.
```
$ head index_list
10765621 ACGTACTGTG
9006389 AACCACGCTT
6891089 ACACCGTTGC
5198342 AGAAGCCATT
4202651 AATCGAGGTG
3788448 ACCTTGTGCA
3271929 ACGAGTTGCA
3027755 ACCGATTGCA
2682797 ACTATCCGTG
54372 ACGTANTGTG
...
```
This may become a blogpost at some point.
