Summarizes some common problems with pointers error-prone (iii)

Pointers and strings

　　Null and NUL difference: The former is used to represent a special pointer ((void*) 0), and Nul is a char (), not mixed.

Character constants: single quotes; strings: double quotes;

How a string is declared: literal, character array, pointer.

string literal pool:

　　　　　　

String initialization

Initialize char array: char header[]= "Media Player";

　　　　

strcpy function Initialization Array

Char header[13];

strcpy (header, "Meadia Player");

2. Initialize the char pointer

char *header; a common way to initialize this string is to use the malloc and strcpy functions to allocate memory and copy the literal to a string.

Char *header= (char*) malloc (strlen ("Media Player") +1);

strcpy (header, "Meadia Player");

The difference between sizeof and strlen:

Standard input initialization string

Standard string manipulation

　　　　　　

#include <stdio.h>#include<stdlib.h>#include"string.h"intMain () {Char* error="ERROR:"; Char* errormessage="Not enough memory"; Char* Buffer= (Char*)malloc(strlen (Error) +strlen (errormessage) +1);     strcpy (Buffer,error);    strcat (buffer, errormessage); printf ("%s", error); printf ("%s\n", errormessage); } 

Passing strings

　　

#include <stdio.h>#include<stdlib.h>#include"string.h"size_t Stringlength (Char*string) {size_t length=0;  while(*(string++) ) {length++; }    returnlength;} intMain () {Char* error="ERROR:"; Char* errormessage="Not enough memory"; Char* Buffer= (Char*)malloc(strlen (Error) +strlen (errormessage) +1);     strcpy (Buffer,error);    strcat (buffer, errormessage); printf ("%s\n", buffer); printf ("%s\n", error); printf ("%s\n", errormessage); printf ("%d\n", buffer); printf ("%d\n", Stringlength (buffer)); } 

Passing a pointer to a character constant

Passing parameters to an application

return string

When a function returns a string, it returns the actual address of the string. The point is how to return a valid address that can return a reference to one of the following three objects: the character amount/dynamically allocated memory/local string variable.

function pointers and strings

Summarizes some common problems with pointers error-prone (iii)