The application of substr function (simple explanation) in C + +

SUBSTR (string, intercept start position, intercept length)//return intercepted word

substr (' Hello World ', 0, 1)//return result is ' H ' * start with a string of length 1 from the first character

substr (' Hello World ', 1, 1)//Returns the result for ' H ' *0 and 1 is the first character that represents the start position of the Intercept

substr (' Hello world ', 2,4)//return result as ' Ello '

substr (' Hello world ', -3,3)//Returns the result as ' rld ' * negative (-i) to indicate the start of the intercept is the left number I character of the right end of the string

Test:

Select substr (' Hello world ', -3,3) value from dual;

Attached: simple usage of substring (INDEX1,INDEX2) in Java

Function: begins to intercept a string of length index2-index1 from a character string index (subscript) of index1.

String str= "Hello World";

System.out.println (str.substring (0,5));

Print Result: Hello

below to the section C code to explain, estimate will understand!

1#include <string.h>2#include <stdio.h>3#include <stdlib.h>4#include <assert.h>5 Char* MYSUBSTR (Char* Srcstr,intOffsetintlength)6 {7Assert (Length >0);8ASSERT (Srcstr! =NULL);9 Ten     intTotal_length = strlen (SRCSTR);//first get the length of the Srcstr One     //after judging the length of the srcstr minus the substr start position to intercept, the remaining length A     //is greater than the length specified, and if it is greater, it can take a substring of length -     //Otherwise, all the remaining strings from the starting position are returned.  -     intReal_length = ((total_length-offset) >= length? Length: (total_length-offset)) +1; the     Char*tmp; -     if(NULL = = (tmp= (Char*)malloc(Real_length *sizeof(Char)))) -     { -printf"Memory overflow. \ n"); +Exit0); -     } +strncpy (TMP, Srcstr+offset, Real_length-1); ATmp[real_length-1] =' /'; at     returntmp; - } - intMain () - { -     CharSrcstr[] ="This is a test string!"; -     Char* tmp = MYSUBSTR (SRCSTR,8,8); inprintf"Test:result =%s\n", TMP); -      Free(TMP); to     return 0; +}

The application of substr function (simple explanation) in C + +