Terminal Command Safety

Detailed patterns and examples for safe terminal command execution in AI agent contexts.

Backtick Hazard — Details

Backticks in terminal command arguments break across all shells:

• bash/zsh: backtick = command substitution (echo "use ls here" executes ls)
• PowerShell: backtick = escape character (echo "use n here"` inserts newline)

Ref: vscode#295620

Safe Pattern (bash)

# Write content to temp file (single-quoted delimiter prevents interpolation)
cat > /tmp/body.md << 'EOF'
## Changes
- Added `MyClass` to the module
- Updated `config.py`
EOF

# Pass file to command
gh pr create --title "My PR" --body-file /tmp/body.md
rm /tmp/body.md

Safe Pattern (PowerShell)

$body = @'
## Changes
- Added `MyClass` to the module
'@
$body | Out-File -Encoding utf8 "$env:TEMP\body.md"
gh pr create --title "My PR" --body-file "$env:TEMP\body.md"
Remove-Item "$env:TEMP\body.md"

Output Capture — Examples

Refs: vscode#308610, vscode#308048, vscode#307173

Redirect to file

npm run build 2>&1 | Out-File -Encoding utf8 "$env:TEMP\build-output.txt"
Get-Content "$env:TEMP\build-output.txt" -Tail 50

Pipe through Out-String

git log --oneline -20 | Out-String

Sentinel pattern

npm test 2>&1; echo "EXIT_CODE:$LASTEXITCODE"

Alt-buffer avoidance

• git log not git log | less (set $env:GIT_PAGER="cat")
• Get-Help not man
• gh issue view --json not gh issue view (which opens a pager)

Terminal Hanging — Examples

Refs: vscode#308610, vscode#306490

Async mode selection

mode=async for: npm start, dotnet run, docker compose up, long test suites
mode=sync with timeout=30000 for: npm install, git operations, single test files

Pre-answer interactive prompts

npm install --yes
rm -rf (not rm -ri)
az login --use-device-code
git commit --no-edit (merge commits)

Network timeouts

npm install --prefer-offline --no-audit
curl --max-time 30 --connect-timeout 10 $url