Open navigation menu

Here Documents and Strings

Uses here documents and here strings to feed multi-line text to commands, generate config files, and create inline data for script processing.

BashConfig Management

Code

snippet
#!/usr/bin/env bash
set -euo pipefail

# Here document: no expansion (quoted delimiter)
cat > /tmp/config.yaml << 'EOF'
server:
  host: localhost
  port: 8080
  timeout: 30

database:
  url: postgres://localhost:5432/mydb
  pool_size: 10

logging:
  level: info
  file: /var/log/app.log
EOF
echo "Config file created"

# Here document: with variable expansion
app_name="MyApp"
version="1.0.0"
cat > /tmp/app.info << EOF
Application: $app_name
Version: $version
Generated: $(date +%Y-%m-%d)
PID: $$
EOF
cat /tmp/app.info

# Here string (single line)
read -r first second third <<< "one two three"
echo "Parsed: $first / $second / $third"

# Here document to function
process_data() {
    while IFS= read -r line; do
        echo "  > $line"
    done
}

process_data << EOF
Line 1: Hello
Line 2: World
Line 3: From Bash
EOF

# Generate script from heredoc
cat > /tmp/generated.sh << 'SCRIPT'
#!/usr/bin/env bash
echo "Generated script running"
echo "Arguments: $@"
SCRIPT
chmod +x /tmp/generated.sh
/tmp/generated.sh arg1 arg2

# Cleanup
rm -f /tmp/config.yaml /tmp/app.info /tmp/generated.sh

Related Examples