File Content Display

cat [filename]

• Display entire file contents
• Simple output to stdout

less [filename]

• View file with pagination
• Navigate with arrows/PgUp/PgDn

head -n [num] [file]

• Show first N lines of file
• Default: 10 lines

tail -n [num] [file]

• Show last N lines of file
• Use -f to follow live updates

Text Searching

grep [pattern] [file]

• Search for text patterns
• Case-sensitive by default

grep -i [pattern] [file]

• Case-insensitive search

grep -r [pattern] [directory]

• Recursive search in directories

Text Manipulation

sed 's/old/new/g' [file]

• Replace text globally
• Use -i for in-place editing

awk '{print $1}' [file]

• Print specific columns
• $1=first column, $2=second, etc

sort [file]

• Sort lines alphabetically
• Use -n for numeric sort

uniq [file]

• Remove duplicate lines
• Often used with sort

Text Filtering

cut -d',' -f1-3 [file]

• Extract specific fields
• -d sets delimiter, -f selects fields

tr 'a-z' 'A-Z' < [file]

• Translate/replace characters
• Example converts to uppercase

Word/Line Counting

wc -l [file]

• Count lines in file

wc -w [file]

• Count words in file

wc -c [file]

• Count characters in file

Example Pipeline

1
2
3
4

cat access.log | grep "ERROR" | \
awk '{print $1, $4}' | \
sort | uniq -c | \
head -10