Counting with wc

The wc command counts lines, words, and characters in files. It's simple but incredibly useful for file analysis.

Basic Usage

wc filename

Output shows: lines, words, characters, filename

Understanding the Output

 10  45  256 file.txt
  │   │    │    │
  │   │    │    └── filename
  │   │    └── characters (bytes)
  │   └── words
  └── lines

wc Options

Option	Shows
-l	Lines only
-w	Words only
-c	Characters (bytes) only
-m	Characters (multi-byte safe)
-L	Longest line length

Exercise: Count Lines

Count the number of lines in a file:

Counting Multiple Files

wc *.txt                    # Each file and total
wc -l *.log                 # Lines in each log

Common Use Cases

Count Lines of Code

wc -l *.py                  # Python files
wc -l src/*.js              # JavaScript files
find . -name "*.js" | xargs wc -l   # Recursive

Count Log Entries

wc -l /var/log/syslog

Check File Size (characters)

wc -c large_file.txt

Combining with Pipes

Count Output Lines

ls | wc -l                  # Number of files
ps aux | wc -l              # Number of processes
grep "error" log.txt | wc -l # Number of errors

Count Unique Items

cat file.txt | sort | uniq | wc -l

Practical Examples

How Many Users?

wc -l /etc/passwd

Lines in All Files

wc -l *.txt

Longest Line

wc -L config.txt            # Useful for column width

Comparison: Different Counts

What you want	Command
Total lines	wc -l file
Non-empty lines	grep -c . file
Lines matching pattern	grep -c pattern file

Key Takeaways

• wc counts lines, words, and characters
• Use -l for just lines (most common)
• Use -w for just words
• Combine with pipes to count command output
• Essential for analyzing text files and logs