Insert a character in a string

[madmars]

Hi!
Lets say I have a string with numbers "123456789". How can I insert commas in the string to make it look like this "123,456,789"?I've tried to realloc the memory every time i needed to insert a comma and then to put the character from the position n to position n+1 and then to insert the comma but it didn't work i got something like 123,56,89(.
Can anyone help me please,I have a deadline till Friday?!

Thanks,
Marius.

[laserlight]

You could use the string length to determine how many commas (n) will have to be inserted. Then you can copy the last 3 characters n places to the right, and then insert a comma before them. Then you copy the next three characters (n-1) places to the right, so on and so forth. (You should copy starting from the end in order to avoid overwriting characters prematurely.)

[madmars]

oke i understand,i had the same idea but what function can i use to copy two characters from the third position to the fifth position,cause i don't know any...

[laserlight]

You could use memmove, but I would just use a loop.

[madmars]

i've done this so far:

for(k=0;k<strlen(alfa.sir);k++)
if((strlen(alfa.sir)-k)%3==0 && k>0){
alfa.sir=(char*)realloc(alfa.sir,(strlen(alfa.sir) +1)*sizeof(char));

and after that i don't know what function to use.
alfa.sir is my string("1234567)

[madmars]

You could use memmove, but I would just use a loop.

oke thx i'll try with memmove.

[madmars]

oke i've tried with memove but i think i've got it wrong...this is what i've done but still it doen't work:

for(k=0;k<strlen(alfa.sir);k++)
        if((strlen(alfa.sir)-k)%3==0 && k>0){
            alfa.sir=(char*)realloc(alfa.sir,(strlen(alfa.sir)+1)*sizeof(char));
            for(j=strlen(alfa.sir)-1;j>k;j--)
                memmove(alfa.sir[strlen(alfa.sir)],alfa.sir[j],1);
            alfa.sir[j]=',';
            }

i think the first two arguments of memove have to be pointers,right?can u help and tell me what i'm doing wrong?

thank you!

[Annihilate]

Try changing to memmove(&alfa.sir[strlen(alfa.sir)],&alfa.sir[j],1);

[codeprada]

there u go....i totally different approach though

#include <stdio.h>
#include <string.h>

int main(){
    char * str = "123454235453425";
    int n_sz = strlen(str), commas;
    if (n_sz % 3 == 0){
        commas = (n_sz / 3) - 1;
    }
    else{
        int mod = n_sz % 3;
        commas = ( n_sz - mod ) / 3;
    }
    n_sz = commas + strlen(str);
    char * new_str = (char *)malloc(n_sz);
    int i = strlen(str) - 1;
    for (; i >= 0; i--){
        if (((strlen(str) - i) % 3 == 0) && i != 0){
            new_str[i + commas] = str[i];
            new_str[i + --commas] = ',';
        }
        else{
            new_str[i + commas] = str[i];
        }
    }
    new_str[n_sz] = '\0';
    printf("%s\n", new_str);
    return 0;
}

[madmars]

Thanks a lot guys it's my first time when I ask help on a forum and you've been very very kind and useful!
Have a great night!