Question

Alright. So I have this program in C where I take a string with arguments and values (Such as: "GO 45 STOP 15"). The goal is to parse the string and place the argument with its corresponding value into a typedef structure to work with later on.

This is what my structure looks like:

typedef struct {
    char* keyword;
    double value;
} parameter;

Here are some copies of my code that I am having issues with.
Both main() and initParams() are in the same file and therefore both have access to the same #defines…

main():

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

#define STR0_SIZE 80
#define LIST_SIZE   4
#define MAX_PARAMS 15

void main(){
int i;

char str0[STR0_SIZE] = "LEFT 45 GO 686 GO 34.3 STOP 56 RIGHT 26";   //Input String
char* wordList[LIST_SIZE]={"GO", "STOP", "LEFT", "RIGHT"};

int num_arg = 0; //Number of arguements in str0 (each space denotes the end of an arg)

parameter* param;
initParams(param);

replaceSpaces(str0, &num_arg);

findWords(param, str0, num_arg);
}

initParams:

void initParams(parameter* param){
int ctr0, ctr1;

param = (parameter*) malloc(MAX_PARAMS * sizeof(parameter));
printf("\n%i\n", sizeof(parameter));
for(ctr0=0;ctr0<MAX_PARAMS;ctr0++){
        param[ctr0].keyword = "";
        param[ctr0].value = 0;
}

}
ok some quick explainations. initParams is for allocating the memory for each of my parameters. I am assuming that I will not have any idea how many parameters will be included in the string and plan on determining the number in the string later in the program. I do know that I will not accept more than parameters in the string.
After allocating the memory, I loop through each one and initialize each value to either an empty string or 0. (I do realize this is probably unnecessary, however I have done this as part of my code troubleshooting.

Continuing on, replaceSpaces() simply loops through the string and replaces each occurrence of ‘ ‘ with a ‘\0’. It also counts the number of arguements present in the string so that I know how many new strings I have just created by adding null terminators.

Now the tricky part in which I am having difficulty.

#define MAX_ARG_LENGTH 20

void findWords(parameter* param, char* str0, int num_arg){
parameter temp[countWords(str0, num_arg)];
int i;
int ctr0,ctr1, ctr2=0;
int word=0; //flag
char tempStr[MAX_ARG_LENGTH]="";
char* c0 = str0;

for(ctr0=0; ctr0<num_arg; ctr0++){
    word=0;
    ctr1=0;
    if(((*c0 > 'a') && (*c0 <'z')) || ((*c0 > 'A') && (*c0 <'Z'))){
        word=1;
        tempStr[ctr1]=*c0;
        ctr1++;
    }
    while(*c0 != '\0'){
        c0++;
        if(word)
            tempStr[ctr1++] = *c0;
        printf("\ntempStr: '%s'\n", tempStr);
    }
    if(word){
        param[ctr2].keyword = tempStr;
        printf("%s\n", param[ctr2].keyword);
        ctr2++;
    }
    c0++;
}
    for(i=0; i<num_arg/2;i++){
        printf("'%s'\n", param[i].keyword);
        printf("'%g'\n", param[i].value);
}


}

This function works properly at finding each word in the string and storing it in tempStr. My issue is with assigning it to my parameter array back in my main(). I have tried assigning them to a temp array of parameters and then setting "param" equal to the temp array. However due to the fact that param is a pointer, when I assign it a local location, after the function is finished, the memory is freed and lost. Enter my idea to use malloc to predefine memory for them and assign it after.

This is my current output when I compile and run the code. I added comments to clarify

16 //sizeof(parameter)

5 //Number of words in str0

LEFT

GO

GO

STOP

RIGHT

‘RIGHT’ //Things in single quotes are prints from the array of parameters

‘8.05316e-315’

‘RIGHT’

‘0’

‘RIGHT’

‘8.04051e-315’

‘RIGHT’

‘0’

‘RIGHT’

‘0’

MAIN: //I printed these in main using the same for loop seen in findWord()

‘▒▒’

‘8.05316e-315’

‘▒▒’

‘0’

‘▒▒’

‘8.04051e-315’

‘▒▒’

‘0’

‘▒▒’

‘0’

If anyone can help me properly assign the contents of tempStr to a parameter in my array declared in main I would be greatly appreciative. Please Let me know if you need any more information.

THANK YOU ALL!! I GOT IT!!!

Rather than make "tempStr" I just assgned the characters directly to the param[index].keyword. It worked like a charm

Thank you guys very much! I had read many different Qs and As here before but this was my first time posting. I am very excited with how quickly you guys were able to reply.

Thanks again!

~Nick

Answer 1

I think you are misunderstanding what param[ctr2].keyword = tempStr; does It does not copy the string in tempstr to keyword it just makes keyword point to tempstr, which means all the keywords will point to the tempStr variable and will be invalid if you access it outside this function.

What you want to do is to make

char* keyword;

into

char keyword[MAX_ARG_LENGTH];

And use something like strcpy or strncpy to do the copying.

You also do not appear to be setting value anywhere