add: grep cmd

cpp/inherit.cpp

@@ -0,0 +1,21 @@
+
+#include <iostream>
+using namespace std;
+class A {
+public:
+	int name;
+	A* copy() {return this;}
+};
+
+class B : public A {
+};
+
+
+int main() {
+	B* b = new B;
+
+	b->name = 3;
+
+	A* obj = b->copy();
+	cout << b->copy()->name << endl;
+}

doc/cmd.md

@@ -658,6 +658,13 @@ Commands                | Description
 `head -c 3 file`          | Print first 3 character of the file
 `head -n 20 file \| tail -10`    | Print lines 10-20
 
+## Grep
+
+`grep -e "sth"`, with `-e`, |, +, ? etc needs to be escaped
+`grep -E "sth`, with -E, no need to escape
+
+
+
 
 ## nohup