Skip to main content
Text processing commands provide powerful tools for searching, transforming, and analyzing text content.

​
Pattern Matching

​
grep

Search text using regular expressions. Usage: grep [options] pattern [file...] Options:
  • -i - Case-insensitive search
  • -v - Invert match (show non-matching lines)
  • -n - Show line numbers
  • -c - Count matching lines
  • -l - List files with matches
  • -r - Recursive search
  • -w - Match whole words only
  • -E - Extended regex (default in Lifo)
Examples: 
# Simple search
grep "error" logfile.txt

# Case-insensitive
grep -i "warning" logfile.txt

# With line numbers
grep -n "TODO" src/main.js

# Count matches
grep -c "function" script.js

# Recursive search
grep -r "import" src/

# Multiple files
grep "class" *.js

# Invert match
grep -v "#" config.txt

# Word boundaries
grep -w "test" file.txt
Output example: 
$ grep -n "error" app.log
42:Error: Connection timeout
87:Fatal error: Out of memory
156:Error: File not found

​
sed

Stream editor for text transformation. Usage: sed [options] 'expression' [file...] Options:
  • -i - Edit files in-place
  • -e - Add script expression
Expressions:
  • s/pattern/replacement/ - Substitute
  • s/pattern/replacement/g - Substitute all occurrences
  • s/pattern/replacement/i - Case-insensitive substitute
  • d - Delete lines
  • p - Print lines
Examples: 
# Replace first occurrence
sed 's/old/new/' file.txt

# Replace all occurrences
sed 's/old/new/g' file.txt

# Case-insensitive replace
sed 's/error/warning/gi' log.txt

# Delete lines matching pattern
sed '/^#/d' config.txt

# In-place editing
sed -i 's/http:/https:/g' urls.txt

# Multiple expressions
sed -e 's/foo/bar/' -e 's/baz/qux/' file.txt
Output example: 
$ echo "hello world" | sed 's/world/universe/'
hello universe

​
awk

Pattern scanning and processing language. Usage: awk [options] 'program' [file...] Options:
  • -F sep - Field separator (default: whitespace)
Built-in variables:
  • $0 - Entire line
  • $1, $2, ... - Field values
  • NR - Line number
  • NF - Number of fields
Examples: 
# Print specific field
awk '{print $2}' data.txt

# Print multiple fields
awk '{print $1, $3}' data.txt

# Custom field separator
awk -F',' '{print $2}' data.csv

# Pattern matching
awk '/error/ {print $0}' log.txt

# Line numbers
awk '{print NR, $0}' file.txt

# BEGIN and END blocks
awk 'BEGIN {sum=0} {sum+=$1} END {print sum}' numbers.txt

# Conditional printing
awk '$3 > 100 {print $1, $3}' data.txt
Output example: 
$ echo -e "a 1\nb 2\nc 3" | awk '{print $2, $1}'
1 a
2 b
3 c

​
Line Selection

Output the first part of files. Usage: head [options] [file...] Options:
  • -n NUM - Output first NUM lines (default: 10)
Examples: 
# First 10 lines
head file.txt

# First 5 lines
head -n 5 file.txt

# Multiple files
head -n 3 file1.txt file2.txt

​
tail

Output the last part of files. Usage: tail [options] [file...] Options:
  • -n NUM - Output last NUM lines (default: 10)
Examples: 
# Last 10 lines
tail file.txt

# Last 20 lines
tail -n 20 file.txt

# View end of log
tail -n 50 app.log

​
Sorting and Filtering

​
sort

Sort lines of text. Usage: sort [options] [file...] Options:
  • -r - Reverse order
  • -n - Numeric sort
  • -u - Unique (remove duplicates)
  • -k N - Sort by field N
Examples: 
# Alphabetical sort
sort names.txt

# Reverse sort
sort -r names.txt

# Numeric sort
sort -n numbers.txt

# Remove duplicates
sort -u list.txt

# Sort by second field
sort -k 2 data.txt

​
uniq

Report or filter repeated lines. Usage: uniq [options] [file] Options:
  • -c - Count occurrences
  • -d - Only show duplicates
  • -u - Only show unique lines
Examples: 
# Remove adjacent duplicates
uniq file.txt

# Count occurrences
uniq -c file.txt

# Show only duplicates
uniq -d file.txt

# Show only unique
uniq -u file.txt

# Common pattern: sort then uniq
sort file.txt | uniq -c
Output example: 
$ sort animals.txt | uniq -c
   3 cat
   1 dog
   2 fish

​
Text Manipulation

​
cut

Remove sections from lines. Usage: cut [options] [file...] Options:
  • -d delim - Field delimiter
  • -f list - Select fields (e.g., 1, 1-3, 1,3)
  • -c list - Select characters
Examples: 
# Extract first field
cut -d',' -f1 data.csv

# Multiple fields
cut -d',' -f1,3 data.csv

# Field range
cut -d':' -f1-3 /etc/passwd

# Character positions
cut -c1-10 file.txt

​
tr

Translate or delete characters. Usage: tr [options] set1 [set2] Options:
  • -d - Delete characters
  • -s - Squeeze repeated characters
Examples: 
# Uppercase to lowercase
echo "HELLO" | tr 'A-Z' 'a-z'

# Delete characters
echo "hello123" | tr -d '0-9'

# Squeeze spaces
echo "hello  world" | tr -s ' '

# Replace characters
echo "hello" | tr 'el' 'ip'

​
rev

Reverse lines characterwise. Usage: rev [file...] Examples: 
# Reverse each line
echo "hello" | rev
# Output: olleh

rev file.txt

​
tac

Concatenate and print files in reverse. Usage: tac [file...] Examples: 
# Reverse line order
tac file.txt

# Reverse log file
tac application.log

​
Line Processing

​
wc

Count lines, words, and characters. Usage: wc [options] [file...] Options:
  • -l - Count lines only
  • -w - Count words only
  • -c - Count characters only
Examples: 
# All counts
wc file.txt

# Line count only
wc -l file.txt

# Word count
wc -w file.txt

# Character count
wc -c file.txt

# Multiple files
wc -l *.txt
Output example: 
$ wc file.txt
  42  256  1847 file.txt

​
nl

Number lines of files. Usage: nl [options] [file...] Options:
  • -b a - Number all lines
  • -b t - Number non-empty lines only
Examples: 
# Number all lines
nl file.txt

# Number non-empty lines
nl -b t file.txt

​
seq

Print numeric sequences. Usage: seq [first] [increment] last Examples: 
# 1 to 10
seq 10

# 5 to 15
seq 5 15

# With increment
seq 0 5 100

# Negative sequence
seq 10 -1 1

​
File Comparison

​
diff

Compare files line by line. Usage: diff [options] file1 file2 Options:
  • -u - Unified format
  • -c - Context format
  • -q - Brief (report only if files differ)
Examples: 
# Compare files
diff old.txt new.txt

# Unified format
diff -u original.txt modified.txt

# Quick check
diff -q file1.txt file2.txt
Output example: 
$ diff old.txt new.txt
3c3
< old line
---
> new line

​
Encoding

​
base64

Base64 encode/decode data. Usage: base64 [options] [file] Options:
  • -d - Decode data
Examples: 
# Encode
echo "hello" | base64

# Decode
echo "aGVsbG8K" | base64 -d

# Encode file
base64 image.png > image.b64

# Decode file
base64 -d image.b64 > image.png

​
strings

Print printable character sequences. Usage: strings [file...] Examples: 
# Extract readable text from binary
strings binary_file

# Find text in executable
strings program.exe | grep "version"

​
Text Editors

​
nano

Simple text editor. Usage: nano [file] Examples: 
# Edit file
nano document.txt

# Create new file
nano newfile.txt

​
less

File pager for viewing text. Usage: less [file] Examples: 
# View file
less document.txt

# Pipe to less
cat large.log | less

​
Common Patterns

​
Extract email addresses

grep -Eo '[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}' file.txt

​
Count word frequency

cat file.txt | tr ' ' '\n' | sort | uniq -c | sort -rn

​
Remove empty lines

grep -v '^$' file.txt

​
Extract specific columns from CSV

cut -d',' -f2,4 data.csv

​
Replace text in multiple files

find . -name "*.txt" -exec sed -i 's/old/new/g' {} \;

​
Line count by extension

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

Build docs developers (and LLMs) love

Get started for freeTalk to us