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+# Bash Error Handling and Safety
+
+## Paranoid mode (`set -e`)
+
+Enable `set -e` so the script exits on any unexpected non-zero status. Temporarily disable it around commands that are allowed to fail.
+
+```bash
+set -e
+
+some_function () {
+    # ... critical code ...
+
+    set +e
+    grep ... || true
+    local -i ec=$?
+    set -e
+
+    if (( ec != 0 )); then
+        : # handle expected non-match
+    fi
+}
+```
+
+## `pipefail`
+
+Use `set -o pipefail` so the pipeline returns the status of the last command that exited non-zero, not just the last command.
+
+```bash
+set -o pipefail
+command1 | command2 | command3
+```
+
+## `PIPESTATUS`
+
+Capture `PIPESTATUS` into an array immediately after a pipeline to inspect each stage's exit code.
+
+```bash
+tar -cf - ./* | ( cd "$dir" && tar -xf - )
+return_codes=("${PIPESTATUS[@]}")
+if (( return_codes[0] != 0 )); then
+    echo 'tar failed' >&2
+fi
+```
+
+## Arithmetic and Comparisons
+
+Use arithmetic evaluation `(( ))` or numeric comparison operators (`-gt`, `-lt`, `-eq`) to avoid unintended lexicographical comparison.
+
+```bash
+# Wrong: lexicographical
+if [[ "$my_var" > 3 ]]; then
+
+# Right: numeric
+if (( my_var > 3 )); then
+if [[ "$my_var" -gt 3 ]]; then
+```
+
+## Restricted Bash
+
+Use `rbash` as a coarse sandbox for highly constrained environments.
+
+```bash
+rbash -c 'echo hi'
+```
+
+See `man bash` (RESTRICTED SHELL) for details and caveats.