bzip2

Overview

The bzip2 command compresses files using the Burrows-Wheeler block sorting text compression algorithm. It typically achieves better compression ratios than gzip but uses more CPU time.

Syntax

bzip2 [options] [file...]
bunzip2 [options] [file...]
bzcat [file...]

Common Options

Option	Description
`-c`	Write to stdout
`-d`	Decompress
`-f`	Force overwrite
`-k`	Keep original files
`-q`	Quiet mode
`-v`	Verbose output
`-t`	Test integrity
`-1` to `-9`	Compression level
`-s`	Small memory usage
`--fast`	Same as -1
`--best`	Same as -9

Compression Levels

Level	Description
`-1`	Fastest compression
`-6`	Default compression
`-9`	Best compression
`--fast`	Fastest (same as -1)
`--best`	Best (same as -9)

Key Use Cases

High-ratio file compression
Archive preparation
Backup compression
Bandwidth-limited transfers
Long-term storage

Examples with Explanations

Example 1: Basic Compression

bzip2 file.txt

Compresses file.txt to file.txt.bz2 and removes original

Example 2: Keep Original

bzip2 -k file.txt

Compresses file but keeps the original

Example 3: Decompress

bunzip2 file.txt.bz2

Decompresses file back to original

Example 4: Best Compression

bzip2 -9 largefile.txt

Uses maximum compression level

Understanding Compression

Compression characteristics: - Better ratios than gzip - Slower than gzip - Good for text files - Block-based compression - Memory usage varies by level

Common Usage Patterns

Compress to stdout:
```
bzip2 -c file.txt > file.txt.bz2
```
Test compressed file:
```
bzip2 -t file.txt.bz2
```
Verbose compression:
```
bzip2 -v file.txt
```

Related Commands

Command	Description
`bunzip2`	Decompress bzip2 files
`bzcat`	View compressed files
`bzgrep`	Search compressed files
`bzless`	Page through compressed files
`bzdiff`	Compare compressed files

Advanced Usage

Small memory mode:
```
bzip2 -s file.txt
```
Force compression:
```
bzip2 -f existing.txt.bz2
```
Quiet operation:
```
bzip2 -q *.txt
```

Performance Analysis

CPU intensive compression
Excellent compression ratios
Memory usage: 400k + (8 × block size)
Good for archival storage
Consider time vs space trade-offs

File Extensions

Extension	Description
`.bz2`	Standard bzip2
`.tbz`	Tar + bzip2
`.tbz2`	Tar + bzip2
`.tar.bz2`	Tar + bzip2

Best Practices

Use for long-term storage
Consider CPU vs compression trade-offs
Test compressed files
Keep originals for critical data
Use appropriate compression levels

Integration Examples

With tar:
```
tar -cjf archive.tar.bz2 directory/
```

Backup compression:

mysqldump database | bzip2 > backup.sql.bz2

Log compression:

find /var/log -name "*.log" -mtime +7 -exec bzip2 {} \;

Scripting Applications

Automated compression:

#!/bin/bash
for file in *.txt; do
    bzip2 -k "$file"
    echo "Compressed: $file"
done

Space-saving backup:

backup_compress() {
    local source="$1"
    local dest="$2"
    tar -c "$source" | bzip2 -9 > "$dest.tar.bz2"
}

Memory Usage

Block sizes and memory usage: - Block size 100k: ~1.2MB memory - Block size 200k: ~2.4MB memory - Block size 900k: ~10.8MB memory - Use -s for reduced memory usage

Troubleshooting

Out of memory errors
Corrupted compressed files
Slow compression speed
Disk space issues
Permission problems

Comparison with Other Tools

Tool	Speed	Ratio	CPU Usage
gzip	Fast	Good	Low
bzip2	Medium	Better	Medium
xz	Slow	Best	High

Security Considerations

Verify file integrity after compression
Test decompression before deleting originals
Check available disk space
Monitor compression processes
Validate compressed file sources