grep "pattern" file.txt
# searches for pattern in file

grep -i "pattern" file.txt
# ignores case (case-insensitive search)

grep -R "pattern" /path
# recursively searches all files in the given path

grep -n "pattern" *.txt
# shows matching lines with line numbers

grep -v "^#" file.txt
# shows all lines that do not start with # (filters out comments)

grep -c "pattern" file.txt
# returns the number of matches; if given a directory, counts per file

grep -l "pattern" /path
# lists each file that contains at least one match (only once per file)

grep -w "pattern" file.txt
# matches the pattern as a whole word

grep --color=auto "pattern" file.txt
# highlights matches in color

grep -A 2 "pattern" file.txt
# shows 2 lines **after** each match

grep -B 2 "pattern" file.txt
# shows 2 lines **before** each match

grep -C 2 "pattern" file.txt
# shows 2 lines of context before and after each match

grep -E "pattern1|pattern2|pattern3" file.txt
# shows all lines that contain at least one of the 3 patterns

grep "pattern1" file.txt | grep "pattern2" | grep "pattern3"
# shows only lines that contain **all 3** patterns (logical AND)

awk '/pattern1/ && /pattern2/ && /pattern3/' file.txt
# alternative way for AND search, case-sensitive

grep -Rin "pattern" /path
# recursive, case-insensitive search with line numbers

grep -Ril "pattern" /path
# recursive, case-insensitive, lists matching filenames only (once)