What are grep options?

Here are some commonly used grep options:

-i: Perform case-insensitive searching.
```
grep -i "pattern" filename
```
-c: Count the number of matching lines.
```
grep -c "pattern" filename
```
-n: Display line numbers along with matching lines.
```
grep -n "pattern" filename
```
-v: Invert the match, showing lines that do not match the pattern.
```
grep -v "pattern" filename
```
-r or -R: Recursively search through directories.
```
grep -r "pattern" directory/
```
-l: Show only the names of files with matching lines.
```
grep -l "pattern" *
```
-e: Specify multiple patterns to search for.
```
grep -e "pattern1" -e "pattern2" filename
```

These options can be combined to enhance the search capabilities of grep.