process-substitution-fifos

## CRITICAL GUIDELINES

### Windows File Path Requirements

**MANDATORY: Always Use Backslashes on Windows for File Paths**

When using Edit or Write tools on Windows, you MUST use backslashes (`\`) in file paths, NOT forward slashes (`/`).

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# Process Substitution & FIFOs (2025)

## Overview

Master advanced inter-process communication patterns in bash using process substitution, named pipes (FIFOs), and efficient data streaming techniques. These patterns enable powerful data pipelines without temporary files.

## Process Substitution Basics

### Input Process Substitution `<(command)`

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

# Compare two command outputs
diff <(sort file1.txt) <(sort file2.txt)

# Compare remote and local files
diff <(ssh server 'cat /etc/config') /etc/config

# Merge sorted files
sort -m <(sort file1.txt) <(sort file2.txt) <(sort file3.txt)

# Read from multiple sources simultaneously
paste <(cut -f1 data.tsv) <(cut -f3 data.tsv)

# Feed command output to programs expecting files
# Many programs require filename arguments, not stdin
wc -l <(grep "error" *.log)

# Process API response with tool expecting file
jq '.items[]' <(curl -s "https://api.example.com/data")

# Source environment from command output
source <(aws configure export-credentials --format env)

# Feed to while loop without subshell issues
while IFS= read -r line; do
    ((count++))
    process "$line"
done < <(find . -name "*.txt")
echo "Processed $count files"  # Variable survives!
```

### Output Process Substitution `>(command)`

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

# Write to multiple destinations simultaneously (tee alternative)
echo "Log message" | tee >(logger -t myapp) >(mail -s "Alert" admin@example.com)

# Compress and checksum in one pass
tar cf - /data | tee >(gzip > backup.tar.gz) >(sha256sum > backup.sha256)

# Send output to multiple processors
generate_data | tee >(processor1 > result1.txt) >(processor2 > result2.txt) > /dev/null

# Log and pro