Summary of String Copy, Concatenation, Comparison and Split Functions (1)

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Note: When using string processing functions, be sure to start with #include

1.strcpy() function

Prototype declaration: char strcpy(char dest, const char *src);

Function: put string is copied to the address space starting with dest
Note: The memory areas pointed to by src and dest cannot overlap and dest must haveenough space to hold the string of src.
Returns a pointer to dest.

#include int main(){char str01[50]="happy birthday to you";char str02[50];char *p=NULL;p=strcpy(str02,str01);puts(p);int i;str02[i+21]=' ';for(i=0;i<4;i++)str02[i+22]='a'+i;//Add the character 'a' after the str02 character, and add 3 characters in a loopstr02[i+22]='\0';//Add a string end mark '\0' after the characterputs(str02);return 0;}

Running result:

2. String concatenation function

The form is: strcat(character array 1, character array 2) - a function of string concatenation

The effect is to put the String concatenate, concatenate string 2 to the back of string 1, and place the result in character array 1.

#include int main(){char str01[100]="strcat test! ";char str02[100]="str02 to str01";puts(str01);puts(str02);strcat(str01, str02);//Append the contents of str01 to str02puts(str01);return 0;}

Run result:

3, string comparison function

The form is: strcmp(character array 1, string 2) - a function of string comparison

Because strings cannot use the equal sign to compare the size, use the strcmp function to compare!!!!!!

Comparison rules:

(1) If all characters are the same, the two strings are considered equal;

(2) If there are different characters, the comparison result of the first pair of different characters shall prevail.('a' < 'z'; 'A' < 'Z').

The result of the comparison is brought back by the function value:

(3) If string 1 is the same as string 2, the function value is 0.

#include int main(){/*Judgment criteria: When the strings of s1 and s2 are equal, return 0s1>s2, when the first occurrence of a character in s1 is greater than the character in s2vice versa*/char s1[]="happy new day!";char s2[]="happy new day!";char s3[]="hbppy new day!";char s4[]="aappy new day!";int ret=-1;ret = strcmp(s1,s2);printf("%d\n",ret);ret = strcmp(s1,s3);printf("%d\n",ret);ret = strcmp(s1,s4);printf("%d",ret);return 0;}

Run result:

4. String cutting function

Function prototype: char *strtok(char *s, char *delim);

Function function: split the string s according to the string delim, and then return the split result.

Function usage says:

1. The essence of the strtok function is, strtok finds the characters contained in delim in s and replaces it with NULL('/0'), until the whole string is searched.This sentence has two meanings: (1) Each time the strtok function is called, only one division unit can be obtained.(2) To obtain all the division units, the strtok function must be called repeatedly.

2. Subsequent calls to the strtok function need to replace s with NULL.

3. The variable corresponding to the formal parameter s (string to be split) should be in the form of char s[]=”….”, but not in the form of char *s=”….”.

#include int main(){char s1[]="thappy new year!";char *p=NULL;printf("Character before split: ");puts(s1);printf("Character after splitting: ");p=strtok(s1,"a");puts(p);return 0;}

Running result: