Bash

🔍 grep – Search Text Using Patterns

Syntax:

grep [OPTIONS] PATTERN [FILE...]

Options:

Option	Description
`-i`	Ignore case
`-v`	Invert match
`-r`	Recursive search
`-n`	Show line numbers
`-l`	List matching file names only
`-c`	Count matching lines

Examples:

grep "error" logfile.txt
grep -i "hello" file.txt
grep -rn "TODO" ./src
grep -v "DEBUG" app.log

🧠 awk – Pattern Scanning and Processing Language

Syntax:

awk 'pattern {action}' [FILE...]

Options (within scripts):

Option	Description
`$1`, `$2`, …	Columns/fields
`NF`	Number of fields in a line
`NR`	Current record number
`BEGIN`	Run before processing
`END`	Run after all lines

Examples:

awk '{print $1}' file.txt             # Print first column
awk '/error/ {print $0}' log.txt      # Print lines containing "error"
awk 'BEGIN{print "Start"}'            # Just print "Start"
awk '{sum += $2} END {print sum}' data.txt

🧰 sed – Stream Editor

Syntax:

sed [OPTIONS] 'command' [FILE...]

Common Commands:

Command	Description
`s/pattern/replace/`	Replace text
`d`	Delete lines
`p`	Print lines
`-n`	Suppress default output

Examples:

sed 's/apple/orange/' file.txt
sed 's/foo/bar/g' file.txt
sed -n '/hello/p' file.txt     # Print only lines containing "hello"
sed '2d' file.txt              # Delete 2nd line

✂️ cut – Remove Sections from Lines

Syntax:

cut [OPTIONS] [FILE...]

Options:

Option	Description
`-f`	Specify field number
`-d`	Set delimiter (default: tab)
`-c`	Cut by character position

Examples:

cut -f1 file.txt                     # First tab-separated field
cut -d',' -f2 file.csv               # Second column using comma
cut -c1-5 filename.txt               # First 5 characters of each line

🔃 sort – Sort Lines of Text Files

Syntax:

sort [OPTIONS] [FILE...]

Options:

Option	Description
`-r`	Reverse sort
`-n`	Sort numerically
`-k`	Sort by specific field
`-u`	Remove duplicates

Examples:

sort file.txt
sort -r file.txt
sort -n numbers.txt
sort -k2 file.csv
sort -u names.txt

📉 tail – View End of File

Syntax:

tail [OPTIONS] [FILE...]

Options:

Option	Description
`-n`	Number of lines to show
`-f`	Follow file (real-time updates)

Examples:

tail file.txt
tail -n 20 error.log
tail -f /var/log/syslog

📈 head – View Start of File

Syntax:

head [OPTIONS] [FILE...]

Options:

Option	Description
`-n`	Number of lines to show

Examples:

head file.txt
head -n 15 logfile.log

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