There are two kinds of character strings for C:
A character array
An array can modify one of its values, not the whole array.
#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <stdlib.h>
#include <Windows.h>
// Use character arrays to store strings
void main(a) {
// There are three ways to write it
//\0 represents the end character
char str[] = { 'h'.'e'.'l'.'l'.'o'.'\ 0' };
//char str[6]= { 'h','e','l','l','o' };
//char str[10] = "hello";
printf("%s\n", str);
/ / address
printf("%#x\n", str);
getchar(a); }Copy the codeResult output:
hello
0xb3fb78
Copy the codeA character pointer
A character pointer cannot change any of its values, but can be assigned as a whole. Using pointer addition, in conjunction with the terminator, interception is possible.
void main(a) {
char *str = "how are you？";
printf("%s\n", str);
//str[1] = "w" ; // The character pointer cannot change one of its values
str = "hello world";
printf("%s\n", str);
printf("%#x\n", str);
// Use pointer addition to intercept strings
str += 3; // point to the beginning of the fourth character
while (*str) {
printf("%c", *str);
str++;
}
getchar(a); }Copy the codeResult output:
How are you? hello world 0x97b44 lo worldCopy the codeA common method for strings
Online manual: www.kuqin.com/clib/ Related header files: #include
Strcpy String concatenation
Extern char *strcpy(char *dest,char * SRC);
Function: Copy the null-terminated SRC string to the array indicated by dest.
Note: SRC and dest must not overlap and dest must have enough space to hold the SRC string. Returns a pointer to dest.
For example:
void main(void){
char dest[50];
char *a = "china";
char *b = " is powerful!";
strcpy(dest, a);
strcat(dest, b);
printf("%s\n", dest);
system("pause");
}
Copy the codeResult output:
china is powerful!
Copy the codeSTRCHR Searches for characters in a string
Extern char * STRCHR (char *s,char C);
Find the first occurrence of character C in string s
Description: Returns a pointer to the first occurrence of C, or NULL if c is not present in S.
void main(void){
char *str = "I want go to USA!";
printf("%#x\n", str);
// The pointer to the U element
//str+3
char* p = strchr(str, 'w');
if (p){
printf("Index location: %d\n", p - str);
}
else{
printf("Not found.");
}
system("pause");
}
Copy the codeResult output:
0x877B30 Index Location: 2Copy the codeSTRCHR Searches for characters in a string
Extern char * STRSTR (char *haystack, char *needle);
Function: Find the first occurrence of needle in the string haystack (without comparing the terminator NULL).
Description: Returns a pointer to the position where a needle was first seen, or NULL if no needle was found.
// STRSTR looks for the position where needle first appeared in the string haystack
void main(void){
char *haystack = "I want go to USA!";
char *needle = "to";
// The pointer to the U element
char* p = strstr(haystack, needle);
if (p){
printf("Index location: %d\n", p - haystack);
}
else{
printf("Not found.");
}
system("pause");
}
Copy the codeResult output:
Index position: 10Copy the codeMore usage…
//strset sets all characters in string s to character C
void main(void){
char str[] = "internet change the world!";
_strset(str,'w');
printf("%s\n",str);
system("pause");
}
//strrev reverses the order of all characters in the string s
void main(void){
char str[] = "internet change the world!";
_strrev(str);
printf("%s\n", str);
system("pause");
}
// Atoi string is converted to int
//atol() : converts a string to a long integer value
void main(void){
char* str = "a78";
//int r = atoi(str);
printf("%d\n", r);
system("pause");
}
// The string is converted to double
void main(void){
char* str = "77b8b";
char** p = NULL;
//char* p = str + 2;
// Parameter description: STR is the string to be converted, and endstr is the pointer to the first unconverted character
double r = strtod(str,p);
printf("%lf\n", r);
printf("%#x\n", p);
system("pause");
}
//strupr converts to uppercase
void main(void){
char str[] = "CHINA motherland!";
_strupr(str);
printf("%s\n",str);
system("pause");
}
// Convert to lowercase
void mystrlwr(char str[],int len){
int i = 0;
for (; i < len; i++){
/ / a-z a-z letters
if (str[i] >= 'A' && str[i] <= 'Z'){
str[i] = str[i]-'A' + 'a'; }}}void main(void){
char str[] = "CHINA motherland!";
mystrlwr(str,strlen(str));
printf("%s\n", str);
system("pause");
}
// Exercise: Delete the specified character in the string
void delchar(char *str, char del){
char *p = str;
while(*str ! ='\ 0') {
if(*str ! = del) { *p++ = *str; } str++; } *p ='\ 0';
}
// Delete the last character
int main(a)
{
char str[] = "vencent ppqq";
delchar(str,'t');
printf("%s\n", str);
system("pause");
}
//Java String replaceAll
//StringBuffer buff.deleteCharAt(buff.length()-1);
// Delete the last character
void main(void){
char str[] = "internet,";
str[strlen(str) - 1] = '\ 0';
printf("%s\n", str);
// Job: Realloc implements the concatenation of StringBuffers rather than opening up a large array at first
// Structure StringBuffer
system("pause");
}
//memcpy copies count bytes from SRC to dest
void main(void){
char src[] = "C,C++,Java";
char dest[20] = {0};
/ / byte
memcpy(dest,src,5);
printf("%s\n",dest);
system("pause");
}
//memchr looks for the character ch from the first count bytes of the memory region referred to by buf.
void main(void){
char src[] = "C,C++,Java";
char ch = 'C';
// bytes (segmented)
char* p = memchr(src+3, ch, 5);
if (p){
printf("Index: %d\n", p - src);
}
else{
printf("Can't find \n");
}
system("pause");
}
//memmove copies count bytes from SRC to dest.
void main(a){
char s[] = "Michael Jackson!";
// Capture the effect
memmove(s, s + 8.strlen(s) - 8 - 1);
s[strlen(s) - 8] = 0;
printf("%s\n", s);
getchar(a); }// Find the position of the first character matching any character in string s2 in string s1, excluding the NULL character
void main(a){
char *s1 = "Welcome To Beijing";
char *s2 = "to";
char *p;
p = strpbrk(s1, s2);
if (p)
printf("%s\n", p);
else
printf("Not Found! \n");
p = strpbrk(s1, "Da");
if (p)
printf("%s", p);
else
printf("Not Found!");
getchar(a); }Copy the code