grep

GREP = Global Regular Expression search & Print

Use cases

• Log analysis: Search log files for errors, warnings, or specific events.
• Configuration file editing: Find and modify specific settings in configuration files.
• Code searching: Locate specific functions, variables, or code patterns in source code.
• Text file processing: Extract or filter specific data from text files.
• System administration: Identify potential issues or monitor system activity by searching log files.

Examples

Find all lines containing "error" in the file "system.log":

grep "error" system.log

Search Multiple Files

Search for "config" in all .txt files in the current directory:

grep "config" *.txt

Case-Insensitive Search

Find all occurrences of "admin" (ignoring case) in the file "users.txt":

grep -i "admin" users.txt

Line Numbers

Print the line numbers and lines containing "root" in "passwd":

grep -n "root" passwd

Regular Expressions

Find all lines starting with a digit in "data.csv":

grep "^[0-9]" data.csv

Counting Matches

Count the number of lines with "warning" in "messages.log" (without showing the lines):

grep -c "warning" messages.log