wc

Overview

The wc (word count) command counts lines, words, characters, and bytes in files or input streams. It’s essential for text analysis and file statistics.

Syntax

wc [options] [file...]

Common Options

Option Description
-l Count lines only
-w Count words only
-c Count bytes only
-m Count characters only
-L Length of longest line
--files0-from=file Read null-separated filenames

Default Output Format

Without options, wc shows:

lines words bytes filename

Example output:

  42  156  892 file.txt

Key Use Cases

  1. Count lines in files
  2. Analyze text statistics
  3. Monitor file growth
  4. Validate data processing
  5. Script automation

Examples with Explanations

Example 1: Basic Count

wc file.txt

Shows lines, words, and bytes count

Example 2: Lines Only

wc -l file.txt

Shows only line count

Example 3: Multiple Files

wc *.txt

Shows counts for all text files plus totals

Understanding Counts

  • Lines: Number of newline characters
  • Words: Sequences of non-whitespace characters
  • Characters: Including multibyte characters
  • Bytes: Raw byte count (may differ from characters)

Common Usage Patterns

  1. Count log entries:

    wc -l /var/log/syslog

  2. Monitor file growth:

    watch "wc -l growing_file.log"

  3. Pipeline counting:

    ps aux | wc -l

Advanced Usage

  1. Longest line length:

    wc -L file.txt

  2. Character vs byte count:

    wc -m file.txt  # characters
wc -c file.txt  # bytes

  3. Multiple file totals:

    wc -l *.log

Pipeline Integration

  1. Count command output:

    ls | wc -l

  2. Count unique lines:

    sort file.txt | uniq | wc -l

  3. Count pattern matches:

    grep "error" log.txt | wc -l

Performance Analysis

  • Very fast operation
  • Efficient for large files
  • Minimal memory usage
  • Good pipeline performance
  • Streaming capability

Additional Resources

Best Practices

  1. Use specific options for clarity
  2. Combine with other text tools
  3. Consider character encoding
  4. Use in scripts for validation
  5. Monitor with watch for real-time updates

Scripting Examples

  1. File size validation:

    if [ $(wc -l < file.txt) -gt 1000 ]; then
    echo "File too large"
fi

  2. Progress monitoring:

    TOTAL=$(wc -l < input.txt)
echo "Processing $TOTAL lines"

  3. Log rotation trigger:

    [ $(wc -l < logfile) -gt 10000 ] && logrotate config

Character Encoding

Difference between -c and -m: - -c counts bytes - -m counts characters (important for UTF-8)

Example with Unicode:

echo "café" | wc -c  # 5 bytes
echo "café" | wc -m  # 4 characters

Common Patterns

  1. Count non-empty lines:

    grep -c "." file.txt

  2. Count files in directory:

    ls -1 | wc -l

  3. Count unique users:

    cut -d: -f1 /etc/passwd | wc -l

Integration Examples

  1. With find:

    find . -name "*.py" -exec wc -l {} + | tail -1

  2. With xargs:

    find . -name "*.txt" | xargs wc -l

  3. Log analysis:

    tail -f access.log | while read line; do
    echo "Total requests: $(wc -l < access.log)"
done

Troubleshooting

  1. Binary files giving unexpected results
  2. Character encoding issues
  3. Very large files
  4. Empty files
  5. Permission problems

Real-world Applications

  1. Code metrics:

    find . -name "*.py" | xargs wc -l | tail -1

  2. Data validation:

    [ $(wc -l < data.csv) -eq $(wc -l < expected.csv) ]

  3. Monitoring:

    wc -l /var/log/messages | awk '{print $1}' > line_count.txt