Search text inside files
grep PATTERN FILE
Finds lines matching PATTERN in FILE
-i Case-insensitive search-r Recursive search in directories-n Show line numbers--color=auto Highlight matches in color-v Invert match (exclude pattern)-c Count matching lines-l Show only filenames with matches-w Match whole words only-E Use extended regex-A NUM Show NUM lines after match-B NUM Show NUM lines before match-C NUM Show NUM lines before and after
grep "text" file.txt
Finds lines containing "text" in file.txt
Find all Python files containing a pattern
grep -r "import pandas" . --include="*.py"
Searches for "import pandas" only in .py files
Search with regular expressions
grep -E "error|warning|critical" logfile.txt
Matches lines containing error OR warning OR critical
Find files containing pattern and show filenames only
grep -rl "TODO" .
Lists only the filenames containing "TODO"
Combine with other commands
ps aux | grep python
Searches for Python processes
Search for whole words only
grep -w "test" file.txt
Matches "test" but not "testing" or "latest"