wc — Counting

Line, word, and byte counting — the measurement tool behind wc -l < file, find | wc -l, and file size checks.

Line Count — -l

Count lines in a file

wc -l /etc/passwd

Count lines from stdin — common in pipelines

grep -c "error" /var/log/syslog    # grep -c is often better than grep | wc -l

Why grep -c beats grep | wc -l — one process instead of two

# Slower: spawns two processes, pipes between them
grep "pattern" file | wc -l

# Faster: grep counts internally
grep -c "pattern" file

Word Count — -w

Count words in a file

wc -w document.txt

Count words in a pipeline

echo "four words are here" | wc -w

Character Count — -m

Count characters (multibyte-aware)

wc -m document.txt

Difference between -m and -c matters for UTF-8

printf 'caf\xc3\xa9\n' | wc -m    # 5 characters (e-acute is one char)
printf 'caf\xc3\xa9\n' | wc -c    # 6 bytes (e-acute is two bytes)

Byte Count — -c

Count bytes — file size in bytes

wc -c binary.dat

Quick file size check without ls or stat

wc -c < /var/log/syslog    # No filename in output when using stdin redirect

Max Line Length — -L

Find the longest line in a file — useful for format validation

wc -L /etc/passwd

Check if any lines exceed 80 characters — code style enforcement

wc -L script.sh    # If output > 80, investigate:
awk 'length > 80 {printf "%4d (%d chars): %s\n", NR, length, $0}' script.sh

Multiple Files

Count lines in multiple files — wc totals them automatically

wc -l /var/log/syslog /var/log/auth.log /var/log/kern.log

Suppress the "total" line — useful in scripts

wc -l /var/log/*.log 2>/dev/null | awk '$2 != "total"'

Sort files by line count — find the biggest logs

wc -l /var/log/*.log 2>/dev/null | sort -rn | head -10

Combined with find/xargs — Project Statistics

Count total lines of code in a project — all .sh files

find ~/project -name "*.sh" -type f | xargs wc -l | tail -1

Lines of code per file — sorted by size

find ~/project -name "*.py" -type f -print0 | xargs -0 wc -l | sort -rn | head -20

Count non-blank, non-comment lines (effective lines of code)

find ~/project -name "*.sh" -type f -exec awk '/^[[:space:]]*$/{next} /^[[:space:]]*#/{next} {n++} END{printf "%6d %s\n",n,FILENAME}' {} \; | sort -rn

Count files by extension in a project

find ~/project -type f | awk -F'.' '{print $NF}' | sort | uniq -c | sort -rn

Total lines across all AsciiDoc files

find docs/ -name "*.adoc" -type f -print0 | xargs -0 wc -l | tail -1

Practical Patterns

Quick sanity check — did the filter reduce or increase line count?

echo "before:"; wc -l < data.txt
echo "after:";  grep -v '^#' data.txt | wc -l

Empty file check — zero lines means empty or missing content

find /etc/cron.d -type f -exec sh -c '[ "$(wc -l < "$1")" -eq 0 ] && echo "empty: $1"' _ {} \;

Count unique lines — combine with sort and uniq

sort data.txt | uniq | wc -l

wc with no flags — shows lines, words, bytes all at once

wc /etc/passwd
# Output: lines  words  bytes  filename

Count arguments or items — wc -w on a single-line list

echo "$PATH" | tr ':' ' ' | wc -w    # Number of PATH directories