Command documentation sourced from the linux-command project This comprehensive command reference is part of the linux-command documentation project.

arj - ARJ Archive Manager

The arj command is a powerful archive manager that creates and manages ARJ (Archive by Robert Jung) format compressed files. ARJ was one of the most popular compression formats in the early 1990s, known for its excellent compression ratios, multi-volume support, and robust error recovery capabilities. While largely superseded by modern formats like ZIP and 7z, ARJ remains important for legacy systems and data recovery scenarios.

Historical Context

ARJ was developed by Robert Jung in 1992 as a successor to the ARC format. It gained popularity due to:

• Superior compression ratios compared to early ZIP versions
• Advanced features like self-extracting archives
• Multi-volume support for large file distribution
• Strong error recovery and repair capabilities
• Password protection and file encryption

Basic Syntax

arj [command] [switches] <archive_name> [files...] [-<switches>]

Core Commands

Archive Operations

• a - Add files to archive
• m - Move files to archive (delete originals)
• u - Update files in archive (add new or modified files)
• f - Freshen archive (update only existing files)

Extraction Operations

• x - Extract files with full paths
• e - Extract files without paths (flatten structure)
• t - Test archive integrity

Management Operations

• l - List archive contents (brief)
• v - List archive contents (verbose with details)
• d - Delete files from archive
• r - Rename files in archive
• c - Comment archive
• y - Copy archive with new options
• j - Join multiple volumes

Information Operations

• i - Check archive integrity and show information

Compression Methods and Levels

Method Selection (-m switch)

arj a -m[0-4] archive.arj files/

Method	Compression Level	Speed	Ratio	Best Use Case
-m0	No compression	Fastest	1:1	Already compressed files
-m1	Fastest compression	Very Fast	Good	Quick backups, temporary archives
-m2	Good compression	Fast	Better	General purpose use
-m3	Better compression	Medium	Excellent	Most files, balanced approach
-m4	Best compression	Slowest	Superior	Long-term storage, text files

Advanced Switches

Security and Encryption

• -g - Garble (encrypt) files with password
• -hp - Encrypt both data and headers
• -p[password] - Set password for archive

File Selection

• -r - Recurse into subdirectories
• -a - Include files with archive attribute
• -b - Backup modified files only
• -e[days] - Exclude files older than specified days
• -f[days] - Include files newer than specified days

Volume Management

• -v[size] - Create multi-volume archive
• -va - Auto-detect volume size from media
• -v1440k - Create 1.44MB floppy disk volumes
• -v720k - Create 720KB floppy volumes
• -v1200k - Create 1.2MB 5.25" floppy volumes

Archive Options

• -je - Create self-extracting archive (.exe)
• -jm - Set maximum compression method
• -jd - Disable date/time stamping
• -jt1 - Set temporary directory
• -t1 - Set file type (binary/text)

Recovery and Integrity

• -jg - Add recovery record
• -jg1000 - Add recovery record with 1000 bytes
• -jw - Keep temp files for recovery

Output Control

• -y - Assume Yes for all queries (batch mode)
• -i[log] - Log operations to file
• -n - Process only newer files
• -q - Quiet operation (minimal output)

Usage Examples

Basic Archive Operations

Creating Archives

# Create basic archive
arj a documents.arj file1.txt file2.txt

# Create archive with maximum compression
arj a -m4 backup.arj important_files/

# Create archive recursively including subdirectories
arj a -r project.arj /path/to/project/

# Create archive with specific file types
arj a source.arj *.c *.h *.cpp

# Create archive with date-based selection
arj a -b -f30 recent.arj /data/  # Files modified in last 30 days

Password-Protected Archives

# Create password-protected archive (will prompt for password)
arj a -g secure.arj sensitive_files/

# Create archive with encrypted headers
arj a -hp ultra_secure.arj classified_data/

# Create self-extracting encrypted archive
arj a -je -g installer.exe application_files/

Multi-Volume Archives

# Create 1.44MB floppy disk volumes
arj a -v1440k backup.arj large_dataset/

# Create 100MB volumes for email/CD distribution
arj a -v100m distribution.arj software_package/

# Create volumes with automatic size detection
arj a -va backup.arj /media/usb_drive/

Extraction Operations

Standard Extraction

# Extract with full directory structure
arj x documents.arj

# Extract files to specific directory
arj x backup.arj -/path/to/extract/

# Extract without preserving directory structure
arj e flat_archive.arj

# Extract specific files
arj x project.arj main.c config.h

# Extract with password (will prompt)
arj x -g encrypted.arj

Selective Extraction

# Extract files matching pattern
arj x archive.arj "*.txt"

# Extract to different directory with rename
arj x -/new/location/ -r old.arj

# Extract and verify integrity
arj x -t verified.arj

Archive Management

Content Inspection

# Brief file listing
arj l documents.arj

# Detailed listing with compression info
arj v documents.arj

# List archive information only
arj i documents.arj

# Test archive integrity
arj t documents.arj

# Test with detailed output
arj t -v documents.arj

File Operations

# Add files to existing archive
arj a existing.arj new_file.txt

# Update files in archive (add new or modified)
arj u project.arj updated_sources/

# Freshen existing files only
arj f backup.arj

# Delete files from archive
arj d archive.arj unwanted_file.txt

# Rename files in archive
arj r archive.arj old_name.txt new_name.txt

# Move files to archive (delete originals)
arj m transfer.arj files_to_move/

Practical Applications

System Administration

Backup Strategies

#!/bin/bash
# Daily backup script with ARJ
BACKUP_DIR="/backup"
SOURCE_DIR="/home/user"
DATE=$(date +%Y%m%d)

# Create compressed backup with encryption
arj a -m4 -g -va \
    "$BACKUP_DIR/daily_$DATE.arj" \
    "$SOURCE_DIR" \
    -e"*.tmp" -e"*.cache" -e"*.log"

# Verify backup integrity
if arj t "$BACKUP_DIR/daily_$DATE.arj"; then
    echo "Backup successful and verified"
else
    echo "Backup verification failed"
    exit 1
fi

Log File Management

# Compress old log files
find /var/log -name "*.log.*" -mtime +7 | \
    while read logfile; do
        arj a -m1 -r logs_archive.arj "$logfile"
        rm "$logfile"
    done

# Create monthly log archive
arj a -m2 -b -f30 \
    "logs_$(date +%Y%m).arj" \
    /var/log/ \
    -e"*.log"  # Exclude current logs

Software Distribution

# Create self-extracting installer
arj a -je -m4 \
    installer_v1.0.exe \
    application/ \
    readme.txt \
    license.txt \
    setup.bat

# Create multi-volume distribution for floppies
arj a -v1440k -m3 \
    software_dist.arj \
    software_package/ \
    -e"*.obj" -e"*.tmp"

Data Recovery

Archive Repair

# Test damaged archive
arj t -v damaged.arj

# Extract with error recovery
arj x -jg damaged.arj

# Create recovery record for future repairs
arj a -jg5000 important.arj critical_data/

Volume Recovery

# Join multiple volumes
arj j complete.arj volume1.arj volume2.arj volume3.arj

# Test volume sequence
arj t multi_volume.arj

Legacy System Support

Converting from Modern Formats

# Extract 7z and create ARJ for legacy system
7z x modern_archive.7z
arj a -m4 -r legacy.arj extracted_files/

# Create self-extracting for Windows 3.1
arj a -je -m1 win31_app.exe old_app/

Performance Optimization

Compression Strategy

# Fast compression for temporary archives
arj a -m1 temp.arj files/

# Best compression for long-term storage
arj a -m4 archive.arj documents/

# Selective compression based on file type
arj a -m4 text_files.arj *.txt *.doc *.html
arj a -m1 binary_files.arj *.exe *.jpg *.mp3

Memory and Speed Optimization

# Use temporary directory on fast disk
arj a -t1/tmp arj_file.arj large_dataset/

# Disable file timestamps for speed
arj a -jd fast_backup.arj /data/

# Quiet operation for batch processing
arj a -q -y batch_archive.arj /source/

Multi-threading Considerations

ARJ is single-threaded but can benefit from system optimization:

# Use nice to set priority
nice -n 19 arj a -m4 archive.arj large_files/

# Use ionice for disk I/O priority
ionice -c 3 arj a backup.arj /data/

Error Handling and Troubleshooting

Common Issues

Password Protection Problems

# If password prompt fails, try explicit password
arj x -g"mypassword" archive.arj

# Check if archive is actually encrypted
arj i archive.arj | grep -i encrypt

Volume Issues

# Check volume integrity
arj t -v multi_volume.arj

# Reconstruct missing volumes (if recovery record exists)
arj a -jg new_vol.arj existing_files/

# Join volumes in correct order
arj j complete.arj vol?.arj

Corruption Recovery

# Test archive for errors
arj t -v corrupted.arj

# Extract with recovery enabled
arj x -jg corrupted.arj

# Create new archive from extracted files
arj a -m4 recovered.arj extracted_files/

Space Issues

# Check archive size before extraction
arj i archive.arj

# Extract to different drive with more space
arj x -/mnt/large_disk/ archive.arj

# Use smaller volumes for extraction
arj x -v50m large_archive.arj

Limitations and Workarounds

File Size Limitations

# ARJ has 2GB file size limit
# Split large files before archiving
split -b 1G huge_file.dat huge_part_

# Archive parts separately
arj a -m4 large_file.arj huge_part_*

# Reconstruct after extraction
cat huge_part_* > huge_file.dat

Filename Limitations

# ARJ has limited filename support
# Use tar wrapper for complex filenames
tar cf - complex_filenames/ | arj a -si archive.arj

# Extract with tar wrapper
arj x -so archive.arj | tar xf -

Security Considerations

Password Security

# Avoid passwords in command line (security risk)
# DON'T: arj a -g"password" archive.arj files/
# DO: arj a -g archive.arj files/ (enter password interactively)

# Use strong passwords with mixed characters
# Minimum 8 characters with letters, numbers, symbols

# For automated scripts, use environment variables
ARJ_PASSWORD="$SECURE_PASS" arj a -g archive.arj files/

Encryption Strength

• ARJ uses proprietary encryption (not AES)
• Consider additional encryption for sensitive data:

# Encrypt ARJ with GnuPG
arj a archive.arj files/
gpg -c archive.arj  # Creates archive.arj.gpg

Integration with Other Tools

Shell Script Integration

#!/bin/bash
# Progress indicator for large archives
arj a -m4 large.arj /huge/dataset/ &
PID=$!
while kill -0 $PID 2>/dev/null; do
    echo -n "."
    sleep 10
done
echo "Done!"

Batch Processing

# Process multiple directories
for dir in /data/*/; do
    dirname=$(basename "$dir")
    arj a -m4 -r "$dirname.arj" "$dir"
done

# Compress files by age
find /logs -name "*.log" -mtime +30 -print0 | \
    xargs -0 arj a -m2 old_logs.arj

Cross-Platform Compatibility

Windows Compatibility

# Create Windows-compatible self-extracting archive
arj a -je windows_installer.exe application/

# Use short filenames for Windows 95 compatibility
arj a -jf8 old_win.arj files/

Unix/Linux Integration

# Use with find for selective archiving
find /home -name "*.doc" -print0 | \
    xargs -0 arj a documents.arj

# Pipe operations
tar cf - directory/ | arj a -si archive.arj
arj x -so archive.arj | tar xf -

Migration to Modern Formats

Converting ARJ Archives

#!/bin/bash
# Convert ARJ to 7z format
for arj_file in *.arj; do
    # Extract ARJ
    mkdir temp_extract
    cd temp_extract
    arj x "../$arj_file"

    # Create 7z with better compression
    7z a -m0=lzma2 -mx=9 "../${arj_file%.arj}.7z" *

    cd ..
    rm -rf temp_extract

    # Verify both archives
    arj t "$arj_file"
    7z t "${arj_file%.arj}.7z"
done

Automated Migration Script

#!/bin/bash
# Convert all ARJ archives in directory tree
find . -name "*.arj" | while read arjfile; do
    dir=$(dirname "$arjfile")
    base=$(basename "$arjfile" .arj)

    mkdir -p "$dir/converted"

    # Extract and convert
    (cd "$dir" && \
        mkdir temp && \
        cd temp && \
        arj x "../$base.arj" && \
        7z a "../converted/$base.7z" * && \
        cd .. && rm -rf temp)

    echo "Converted: $arjfile -> $dir/converted/$base.7z"
done

Best Practices

Archive Creation

1. Choose appropriate compression level based on use case
2. Use self-extracting archives for distribution to non-technical users
3. Create multi-volume archives for large file transfers
4. Add recovery records for critical data
5. Use descriptive names with dates or versions

Security Practices

1. Use strong passwords for sensitive archives
2. Avoid passwords in scripts or command history
3. Consider additional encryption for highly sensitive data
4. Test password recovery before distribution
5. Keep password backups in secure location

Performance Optimization

1. Use appropriate compression method for file types
2. Exclude unnecessary files (.tmp, .cache, etc.)
3. Use fast compression for temporary archives
4. Schedule large operations during low-usage periods
5. Monitor disk space during large operations

Maintenance

1. Test archive integrity regularly
2. Verify backups can be restored
3. Migrate to modern formats when possible
4. Document archive passwords securely
5. Keep multiple copies of critical archives

Comparison with Modern Formats

Feature	ARJ	ZIP	7z	tar.gz
Compression Ratio	Good	Fair	Excellent	Good
Speed	Medium	Fast	Slow	Fast
Self-Extracting	Yes	Yes	Yes	No
Multi-Volume	Yes	Limited	Yes	No
Encryption	Proprietary	AES-256	AES-256	GPG
Unicode Support	Limited	Good	Excellent	Excellent
Recovery Record	Yes	No	Yes	No
Modern Support	Limited	Universal	Growing	Universal

Related Commands

• zip - Modern ZIP archive utility
• unzip - Extract ZIP archives
• 7z - 7-Zip archive manager
• tar - Tape archive utility
• gzip - GZIP compression
• bzip2 - BZIP2 compression
• gpg - GNU Privacy Guard for encryption

Performance Tips

1. Use -m1 for speed when compression ratio isn't critical
2. Use -m4 for storage when space is premium
3. Exclude compressed files (.zip, .jpg, .mp3) to save time
4. Use self-extracting archives only when necessary
5. Split large files before archiving if possible
6. Test archives after creation to ensure integrity
7. Use recovery records for mission-critical data
8. Batch operations during off-peak hours

ARJ remains a valuable tool for working with legacy archives and specific use cases requiring its unique features. While modern formats generally offer better performance and compatibility, ARJ's robust error recovery and self-extracting capabilities make it useful for specific applications.