grep1-6  Exercise 1: A Report Script That Dies Without a Word
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(Run in a fresh copy of the practice folder from the chapter. Make it first with the block at the top of the chapter.)

cat > report1.sh <<'EOF'
set -euo pipefail
errors=$(grep -c ERROR app.log)
critical=$(grep -c CRITICAL app.log)
echo "errors=$errors critical=$critical"
EOF
echo "--- the broken script:"
bash report1.sh; echo "exit status: $?"

cat > report2.sh <<'EOF'
set -euo pipefail
errors=$(grep -c ERROR app.log || true)
critical=$(grep -c CRITICAL app.log || true)
echo "errors=$errors critical=$critical"
EOF
echo "--- fixed with || true:"
bash report2.sh; echo "exit status: $?"

cat > report3.sh <<'EOF'
set -euo pipefail
count() { awk -v p="$1" '$0 ~ p { n++ } END { print n + 0 }' app.log; }
echo "errors=$(count ERROR) critical=$(count CRITICAL)"
EOF
echo "--- fixed with awk:"
bash report3.sh; echo "exit status: $?"


Output:

--- the broken script:
exit status: 1
--- fixed with || true:
errors=2 critical=0
exit status: 0
--- fixed with awk:
errors=2 critical=0
exit status: 0

WHY THIS WORKS AS AN ANSWER
---------------------------
The first script stops at the second grep: CRITICAL does not occur, grep -c prints 0 and exits with 1, set -e treats that as a failure inside the command substitution, and the script ends WITHOUT printing anything. The status 1 is the only sign.
'|| true' runs after a failure and succeeds, so the assignment succeeds with the 0 grep had already printed. It keeps grep's own output (0) and hides its status, so it also hides a REAL failure (a missing file would now print an error but carry on).
awk treats 'no matches' as a normal 0 and only fails for a real error, such as a file that cannot be read. The cost is that the pattern is an awk regular expression (extended-style), not grep's, and the line is written differently.