SC2046: Unquoted Command Substitution

Quoting Command Substitutions

Command substitutions with $() or backticks are subject to the same word splitting and globbing rules as regular variable expansion. Unquoted command substitutions can produce unexpected results.

The Problem

# BAD: unquoted command substitution
current_dir=$(pwd)
cd $current_dir  # Breaks if path contains spaces

# GOOD: quoted command substitution
current_dir=$(pwd)
cd "$current_dir"

Real-World Example

# BAD: Breaks on filenames with spaces
for file in $(find . -name "*.log"); do
  echo "Processing $file"
done

# GOOD: Use find -exec or while read
find . -name "*.log" -exec echo "Processing {}" \;

# Or use process substitution with read
while IFS= read -r file; do
  echo "Processing $file"
done < <(find . -name "*.log")

Nested Command Substitutions

One advantage of $() over backticks is clean nesting:

# Clean nesting with $()
echo "Kernel: $(uname -r) on $(hostname)"

# Messy with backticks (requires escaping)
echo "Kernel: \`uname -r\` on \`hostname\`"

When to Leave Unquoted

Intentional splitting of command output into array elements:

# Intentional: populate array from command output
files=($(ls *.txt))  # Note: still problematic with special chars

Even here, a while-read loop is safer for handling arbitrary filenames.