Search & Regex

# Find files by name
find . -name "*.tsx" -type f
find . -name "page.tsx" -path "*/app/*"
 
# Search text inside files
grep -r "useState" src/
grep -rn "TODO" --include="*.ts" .
 
# Faster alternative (ripgrep)
rg "useState" src/
rg "TODO" -t ts
 
# Find and replace across files
sed -i '' 's/oldFunction/newFunction/g' src/**/*.ts

# "Where is this component defined?"
rg "export.*function Header" --include="*.tsx"
# or
grep -rn "export.*function Header" --include="*.tsx" src/
 
# "Which files import this module?"
rg "from.*@/components/Button" -l
# -l = files only, no matching lines
 
# "Find all TODO comments with context"
rg "TODO|FIXME|HACK" -t ts -t tsx -C 2
# -C 2 = show 2 lines of context above and below
 
# "Find large files in the project"
find . -type f -size +1M -not -path "./node_modules/*" -not -path "./.next/*"

# Basic name search (case-sensitive)
find . -name "layout.tsx"
 
# Case-insensitive
find . -iname "readme*"
 
# By file type
find . -type f                   # files only
find . -type d                   # directories only
 
# By extension pattern
find . -name "*.test.ts"
find . -name "*.md" -o -name "*.mdx"  # OR
 
# Exclude directories
find . -name "*.ts" -not -path "*/node_modules/*" -not -path "*/.next/*"
 
# By modification time
find . -name "*.tsx" -mtime -1       # modified in last 24 hours
find . -name "*.tsx" -mmin -60       # modified in last 60 minutes
find . -name "*.tsx" -newer reference.txt  # newer than a file
 
# By size
find . -type f -size +500k           # larger than 500KB
find . -type f -size -1k             # smaller than 1KB
find . -type f -empty                # empty files
 
# Execute a command on results
find . -name "*.test.ts" -exec wc -l {} \;
find . -name "*.log" -exec rm {} \;
find . -name "*.tsx" -exec grep -l "useState" {} \;
 
# Using xargs (often faster for many files)
find . -name "*.ts" | xargs grep "deprecated"
find . -name "*.tmp" -print0 | xargs -0 rm  # handle spaces in filenames

# Basic recursive search
grep -r "pattern" directory/
 
# With line numbers
grep -rn "useState" src/
 
# Case insensitive
grep -rni "error" src/
 
# Only filenames (no matching lines)
grep -rl "useEffect" src/components/
 
# Invert match (lines NOT matching)
grep -v "node_modules" file.txt
 
# Count matches per file
grep -rc "import" src/ | sort -t: -k2 -rn | head -10
 
# Filter by file extension
grep -rn "fetchData" --include="*.ts" --include="*.tsx" .
grep -rn "TODO" --include="*.{ts,tsx}" .
 
# Exclude directories
grep -rn "console.log" --exclude-dir=node_modules --exclude-dir=.next .
 
# Show context around matches
grep -rn "error" -A 3 src/    # 3 lines After
grep -rn "error" -B 2 src/    # 2 lines Before
grep -rn "error" -C 2 src/    # 2 lines Context (both)
 
# Match whole words only
grep -rw "use" src/            # matches "use" but not "useState"
 
# Multiple patterns
grep -rn -e "useState" -e "useEffect" src/

# Install
# macOS: brew install ripgrep
# Ubuntu: sudo apt install ripgrep
 
# Basic search (auto-ignores .gitignore patterns)
rg "pattern" src/
 
# Filter by file type
rg "useState" -t tsx
rg "TODO" -t ts -t tsx
 
# Only filenames
rg "useEffect" -l
 
# Files NOT matching
rg "useEffect" --files-without-match -t tsx
 
# Fixed string (no regex interpretation)
rg -F "array.map((item) =>" src/
 
# Multiline search
rg -U "export default function.*\n.*return" src/
 
# Replace (preview - does not modify files)
rg "oldName" -r "newName"
 
# Show stats
rg "TODO" --stats
 
# Search hidden files too
rg "SECRET" --hidden
 
# Glob patterns
rg "fetch" -g "*.ts" -g "!*.test.ts"  # ts files but not test files

# Anchors
^start        # line starts with "start"
end$          # line ends with "end"
^exact$       # entire line is "exact"
 
# Character classes
[abc]         # a, b, or c
[a-z]         # lowercase letter
[0-9]         # digit
[^abc]        # NOT a, b, or c
.             # any single character
 
# Quantifiers
a*            # zero or more a's
a+            # one or more a's
a?            # zero or one a
a{3}          # exactly 3 a's
a{2,5}        # 2 to 5 a's
 
# Groups and alternation
(foo|bar)     # foo or bar
(abc)+        # one or more "abc" sequences
 
# Common shortcuts
\d            # digit [0-9]        (extended regex)
\w            # word char [a-zA-Z0-9_]
\s            # whitespace
\b            # word boundary
 
# Escape special characters
\.            # literal dot
\(            # literal parenthesis

# Find React component definitions
rg "export (default )?(function|const) [A-Z]\w+"
 
# Find all hook calls
rg "use[A-Z]\w+\(" -t tsx
 
# Find console.log statements (but not console.error/warn)
rg "console\.log\(" src/
 
# Find TODO with author
rg "TODO\([^)]+\):" src/
 
# Find hardcoded URLs
rg "https?://[^\s\"')\]>]+" src/
 
# Find empty catch blocks
rg -U "catch\s*\([^)]*\)\s*\{\s*\}" src/
 
# Find imports from a specific package
rg "from ['\"]react['\"]" src/
 
# Find CSS color hex codes
rg "#[0-9a-fA-F]{3,8}\b" src/
 
# Find potential API keys (basic pattern)
rg "['\"][A-Za-z0-9_]{20,}['\"]" --include="*.ts" src/
 
# Find duplicate adjacent words (typos)
rg "\b(\w+)\s+\1\b" docs/

# Replace in a single file (macOS - '' is required)
sed -i '' 's/oldText/newText/g' file.tsx
 
# Replace in a single file (Linux)
sed -i 's/oldText/newText/g' file.tsx
 
# Preview without modifying (works on both)
sed 's/oldText/newText/g' file.tsx
 
# Replace across multiple files
find src -name "*.tsx" -exec sed -i '' 's/OldComponent/NewComponent/g' {} \;
 
# Replace with regex
sed -i '' 's/className="text-[a-z]*"/className="text-base"/g' file.tsx
 
# Delete lines matching a pattern
sed -i '' '/console\.log/d' src/app/page.tsx
 
# Replace only on lines matching a condition
sed -i '' '/import/s/react/react-dom/' file.tsx

# Print specific columns
ps aux | awk '{print $1, $2, $11}'     # user, PID, command
 
# Sum a column
wc -l src/**/*.tsx | awk '{sum += $1} END {print sum " total lines"}'
 
# Filter by condition
df -h | awk '$5 > "80%"'               # disks over 80% full
 
# Print lines between patterns
awk '/START/,/END/' file.txt
 
# Count unique values
git log --format="%an" | sort | uniq -c | sort -rn