ignore-errors.md

Ignoring errors in a section of a Bash script

For simonw/museums#32 I wanted to have certain lines in my Bash script ignore any errors: lines that used sqlite-utils to add columns and configure FTS, but that might fail with an error if the column already existed or FTS had already been configured.

This tip on StackOverflow lead me to the following recipe:

#!/bin/bash
set -euo pipefail

yaml-to-sqlite browse.db museums museums.yaml --pk=id
python annotate_nominatum.py browse.db
python annotate_timestamps.py
# Ignore errors in following block until set -e:
set +e
sqlite-utils add-column browse.db museums country 2>/dev/null
sqlite3 browse.db < set-country.sql
sqlite-utils disable-fts browse.db museums 2>/dev/null
sqlite-utils enable-fts browse.db museums \
  name description country osm_city \
  --tokenize porter --create-triggers 2>/dev/null
set -e

Everything between the set +e and the set -e lines can now error without the Bash script itself failing.

The failing lines were still showing a bunch of Python tracebacks. I fixed that by redirecting their standard error output to /dev/null like this:

sqlite-utils disable-fts browse.db museums 2>/dev/null