How to Return Char Array?

Question

As you can see I have this code it takes a command (char array ) and divides it into two diffrent arrays if there is "|" between them.What I want is not to print it with the function but return these two new arrays to main and then print them ?

How can I do it ?

#include <fcntl.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <stdlib.h>
#include <unistd.h>

int main()
{
    int a;
    int status,n,i;
    char command[4000];
    write(STDOUT_FILENO,"Shell>",6);
    n=read(STDIN_FILENO,command,4000);
    void getArguments(char **,char*);
    char *getStdOutFileName(char *);
    if(n>0)
    {
        for(i=0;i<n;i++)
        {
            bugrafonk(command,&i);
            printf("%s",First);
            printf("%s",Second);
        }
    }
}

void bugrafonk(char* c,int*length)
{
    int i;
    int a;
    char First[4000];
    char Second[4000];
    for(i=0;i<length;i++)
    {
        if(c[i]=='|')
        {
            i=a;
            for(i=0;i<a;i++)
            {
                char First[i];
            }
            printf("---");
            for(i=a;a<length;i++)
            {
                char Second[i];
            }
        }
    }
    return(First,Second);                   //is this  true ?
}

There are some unnecssery declaration in the main now just avoid them I will use them later on.

Try to build it, read the errors, I mean actually read them (it seems to be to uncommon these days), and fix the errors one by one. Then realize that you can't return a pointer to a local array, as the array like any other local variable will go out of scope once the function returns. — Some programmer dude
– Some programmer dude, Commented May 19, 2015 at 17:04
char* bugrafonk instead of void bugrafonk and return First or return Second instead of return(char First,char Second). — Jared Burrows
– Jared Burrows, Commented May 19, 2015 at 17:04
@JoachimPileborg 95% of the time understanding the meaning of an error message helps both, fixing it, and understanding how things work. — Iharob Al Asimi
– Iharob Al Asimi, Commented May 19, 2015 at 17:06
Btw, turn on compiler warnings, and fix them. For example, you pass length as pointer. Yet you seem to use it as integer. Do you know what a "pointer" is in C? If not, you should probably start simpler... — hyde
– hyde, Commented May 19, 2015 at 17:24

tom · Accepted Answer · 2015-05-19 17:07:30Z

1

To retun char * to main you need to send pointers to your function which are attached to memory that you can use

For example,

....
char return1[50]
char return2[50]
....
split_function(command, return1, return2);
....

answered May 19, 2015 at 17:07

tom

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Aleksei Petrenko · Accepted Answer · 2015-05-19 17:08:36Z

1

The answer depends on where you store the results of your calculations. In your current implementation both First and Second arrays are allocated inside the bugrafonk function and thus will be destroyed when the function is finished.

One possible option would be to allocate memory for result arrays outside the function and pass pointers to the function.

char first[4000], second[4000];
bugrafonk(..., first, second);
// use first and second

And bugrafonk implementation:

void bugrafonk(your arguments..., char *first, char *second)
{
    ...
}

Also, I have no idea what the mysterious word bugrafonk means ;)

answered May 19, 2015 at 17:08

Aleksei Petrenko

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2 Comments

bugra sezer Over a year ago

Anyway so if I didnt send those to arrays as arguments into the function I cant return them ?

Aleksei Petrenko Over a year ago

In C you can return only one variable from function. The usual practice when you have to return many is to pass pointers to variables (or data) as parameters to function, change variables/data inside the function, then just exit. When the function finishes you will have access to you changed data. If you absolutely want to return multiple parameters, have a look at python ;)

Weather Vane · Accepted Answer · 2015-05-19 17:48:12Z

The function implemented here splits the string by terminating the first part, and returns a pointer to the second part.

You don't need to return 2 pieces of information since you already know where the first string is. Note that this will not work if a string literal is passed since you cannot modify it, but that's not the case here.

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

char* bugrafonk(char* c);                   // function prototype

int main(void)
{
    char command[4000];
    char *split;
    scanf("%3999s", command);               // enter limited length string
    split = bugrafonk(command);             // this splits the string
    printf("First part: %s\n", command);    // print first half
    if (split != NULL)                      // if there is a second half
        printf("Second part: %s\n", split); // print second half
}

char* bugrafonk(char* c)                    // returns string pointer
{
    char *cptr = strchr(c, '|');            // find that char
    if (cptr != NULL)                       // if it was found
    {
        *cptr = '\0';                       // terminate first part here
        cptr++;                             // advance pointer to next part
    }
    return cptr;
}

Program output:

one|two
First part: one
Second part: two

Andreas DM · Accepted Answer · 2015-05-19 18:20:10Z

0

You may choose to return a pointer to char, and then pass two arrays that will be modified in the body of the function.:

char *func(char arr[], char* arr2 /* other parameters */)
{   /* process arr and arr2 */        

    // return new array one. arr2 doesn't need to be returned.
    return arr; 
}

// in main:
char command[4000];
char arr2[4000];                  // First
char *arr3 = func(command, arr2); // Second

Or just pass all arrays as arguments to the function and then return void, since they will be modified in the function.

edited May 19, 2015 at 18:20

answered May 19, 2015 at 18:14

Andreas DM

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