CODEWITHSUNDEEP
cscanf
Lauren Walter
Lauren Walter

Reputation: 11

C split string into chunks using sscanf?

I'm trying to write a program to split a string into the first 3 characters, the next 3 characters, and then the last 3 characters for the specific string.

int main(int argc, char *argv[])
{
    char str[9] = "AbcDefGhi";
    char first[3], second[3], third[3];
    int ret;

    ret = sscanf(str, "%3s%3s%3s", first, second, third);
    printf("# variables: %i\n", ret);
    printf("1: %s\n", first);
    printf("2: %s\n", second);
    printf("3: %s\n", third);

    printf("whoops");
    return 0;
}

But when I run it, the output is

# variables: 3                                                                                               
1: AbcDefGhi                                                                                                 
2: DefGhi                                                                                                    
3: Ghi                                                                                                       
whoops

And I want

# variables: 3                                                                                               
1: Abc                                                                                                 
2: Def                                                                                                    
3: Ghi                                                                                                       
whoops

Any help is appreciated.

Upvotes: 1

Views: 560

Answers (2)

kaylum
kaylum

Reputation: 14046

man scanf:

String input conversions store a terminating null byte ('\0') to mark the end of the input; the maximum field width does not include this terminator.

That is, the buffer to store the string needs to be at least one byte larger than the maximum field width to account for the NUL terminator. So increase the size of all your arrays to account for the NUL terminator.

char str[] = "AbcDefGhi";
char first[4], second[4], third[4];

Upvotes: 1

FilipA
FilipA

Reputation: 612

I'm not sure if you need to do it without any functions from libraries, but I have created a code that is doing exactly what you want. Let us know if it's to complicated for you.

#include <stdio.h>
#include <stdlib.h>

char *split(const char *str, size_t size){
    static const char *p=NULL;
    char *temp;
    int i;
    if(str != NULL) p=str;
    if(p==NULL || *p=='\0') return NULL;
    temp=(char*)malloc((size+1)*sizeof(char));
    for(i=0;*p && i<size;++i){
        temp[i]=*p++;
    }
    temp[i]='\0';
    return temp;
}

int main(){
    char *p = "AbcDefGhi";
    char *temp[5];
    int i,j;

    for(i=0;NULL!=(p=split(p, 3));p=NULL)
        temp[i++]=p;

    for(j=0;j<i;++j){
        printf("%d: %s\n",j, temp[j]);
        free(temp[j]);
    }
    printf("whoops");
    return 0;
}

Upvotes: 0

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