Combine filters into a checked summary

Combine filters into a checked summary — guided practice

Count confirmed registrations by session using a pipeline.

Create an empty shell-lab folder. Inside it create input and output folders. Put registrations.tsv in input with these tab-separated rows and a final newline: session<TAB>status; art<TAB>confirmed; code<TAB>confirmed; art<TAB>waiting; code<TAB>confirmed; music<TAB>confirmed. Start the terminal in shell-lab. Bash required; no sudo, remote systems or deletion commands. Start in shell-lab. The status field contains exactly confirmed or waiting.

1. 1. Remove the header

   Run tail -n +2 and inspect the five rows.

   tail -n +2 input/registrations.tsv

   You should see: Only data rows remain.

   The field label must not become a category.

2. 2. Filter status

   Add grep with a Bash-quoted tab followed by confirmed and the end-of-line marker.

   tail -n +2 input/registrations.tsv | grep $'\tconfirmed$'

   You should see: Four confirmed rows remain; the waiting row is absent.

   Matching the tab plus the final status avoids also matching unconfirmed.

3. 3. Count sessions

   Select the first tab-separated field, sort and count adjacent repeated names.

   tail -n +2 input/registrations.tsv | grep $'\tconfirmed$' | cut -f1 | sort | uniq -c

   You should see: art=1, code=2, music=1.

   uniq counts adjacent duplicates, so sorting is necessary.

4. 4. Reconcile

   Add the three counts by hand.

   You should see: 1+2+1=4, matching the filtered row count.

   An independent total catches omissions.