feat: add grep -v falg

Author: jthodge

content/grep/invert-match-with-v-flag.md

@@ -0,0 +1,57 @@
+# grep: Invert Match with -v Flag
+
+The `-v` flag inverts the match to show all lines that do _NOT_ contain the pattern.
+
+```bash
+# Show all lines except those containing "debug"
+grep -v "debug" application.log
+
+# Remove comment lines from config
+grep -v "^#" nginx.conf
+
+# Filter out empty lines
+grep -v "^$" document.txt
+```
+
+## Practical Examples
+
+```bash
+# Show all files except README files
+ls -la | grep -v README
+
+# Find non-successful HTTP status codes
+grep -v "200 OK" access.log
+
+# Remove verbose logging
+tail -f app.log | grep -v "TRACE\|DEBUG"
+```
+
+Filtering test results and system processes:
+
+```bash
+# Show only failed tests
+pytest --tb=short | grep -v "PASSED"
+
+# Find inactive users
+grep -v "active" user_status.csv
+
+# Show processes excluding system ones
+ps aux | grep -v "^root"
+
+# Filter out successful builds
+grep -v "BUILD SUCCESSFUL" ci_logs.txt
+```
+
+Powerful combinations:
+
+```bash
+# Remove comments and empty lines
+grep -v "^#" config.ini | grep -v "^$"
+
+# Exclude multiple patterns
+grep -v -e "INFO" -e "DEBUG" system.log
+
+# Case-insensitive exclusion
+grep -i -v "success" results.txt
+```
+