find, xargs & Parallelism

# Find by name
find /var/log -name "*.log"
find / -type f -name "nginx.conf"

# Find by type
find / -type f          # Files only
find / -type d          # Directories only
find / -type l          # Symlinks only

# Find by size
find / -size +100M      # Larger than 100MB
find / -size -1k        # Smaller than 1KB

# Find by time
find /var/log -mtime -1       # Modified in last 24 hours
find / -mmin -30              # Modified in last 30 minutes
find / -atime +30             # Not accessed in 30 days
find / -ctime -7              # Changed in last 7 days

# Find by permission
find / -perm 777              # Exact permission match
find / -perm -u+s             # Setuid files
find / -perm /o+w             # World-writable files

# Find by owner
find / -user root
find / -nouser               # Orphaned files

# Combine predicates
find / -type f -size +100M -mtime -7 -user root

# Basic xargs: read from stdin, execute command
echo "file1 file2 file3" | xargs rm
find /tmp -name "*.tmp" | xargs rm

# Limit arguments per command
find /var/log -name "*.log" | xargs -n 1 ls -la

# Custom delimiter
echo "one:two:three" | xargs -d: echo

# Show command before executing
find /tmp -name "*.tmp" | xargs -t rm

# Handle empty input
echo "" | xargs -r rm   # -r: don't run if input is empty

# Interactive mode (ask before each command)
find /tmp -name "*.tmp" | xargs -p rm

# DANGEROUS: filenames with spaces break xargs
find . -name "*.txt" | xargs rm    # BREAKS on "file with spaces.txt"

# SAFE: null-delimited output
find . -name "*.txt" -print0 | xargs -0 rm

# -print0 outputs null-delimited filenames
# -0 reads null-delimited input

# Real-world examples
find / -type f -size +100M -print0 | xargs -0 du -sh
find . -name "*.log" -print0 | xargs -0 grep -l "error"

# With GNU find, use -print0 for any user-provided paths
find "$DIR" -print0 | xargs -0 -I{} command {}

# Run 4 parallel jobs
find /var/log -name "*.gz" | xargs -P 4 -I{} gunzip {}

# Parallel compression
find . -type f -name "*.txt" -print0 | xargs -0 -P 8 -I{} gzip {}

# Parallel SSH
cat hosts.txt | xargs -P 10 -I{} ssh {} uptime

# Count available CPUs
NPROC=$(nproc)
find /data -name "*.csv" -print0 | xargs -0 -P $NPROC -I{} process_csv {}

# Monitor parallel jobs
find /data -name "*.csv" -print0 | \
    xargs -0 -P 8 -I{} bash -c 'echo "Processing {}"; process_csv {}; echo "Done {}"'

# DANGEROUS: filenames starting with -
find . -name "*.log" | xargs rm
# If a file is named "-rf /", this executes: rm -rf /

# SAFE: use -- to terminate options
find . -name "*.log" -print0 | xargs -0 rm --

# DANGEROUS: filenames with newlines
echo "file1
file2" | xargs rm  # Treats as one filename

# SAFE: null-delimited
printf "file1\0file2\0" | xargs -0 rm

# DANGEROUS: command injection via filenames
echo 'malicious filename; rm -rf /' | xargs

# SAFE: null-delimited and -0
find . -print0 | xargs -0 -I{} command -- "{}"

# Check for dangerous filenames
find . -print0 | xargs -0 -I{} bash -c 'echo "{}" | grep -q "^-" && echo "DANGER: {}"

# Install parallel
sudo apt install parallel

# Basic parallel execution
cat hosts.txt | parallel ssh {} uptime

# Parallel with output control
cat hosts.txt | parallel --joblog joblog.txt ssh {} uptime

# Limit parallel jobs
parallel -j 4 gzip ::: *.txt

# Use {} as placeholder
find . -name "*.txt" | parallel gzip {}

# Preserve order
find . -name "*.txt" | parallel -k gzip {}

# Show progress
find . -name "*.txt" | parallel --progress gzip {}