How to reset a character array to 0/NULL in C? - c

Question

I am trying to write a program to count letters in every word of a given string and append the count to the word.
Example - I/p: The cake O/p: The3 cake4
In my logic, I want to reset a counter variable named icnt of type integer(which is done) & and an array named temp of type character(which is not working).
I did some research on StackOverflow and implemented memset to reset but looks like it didn't work for me!
Kindly correct my program if there are mistakes.
#include<stdio.h>
#include<string.h>
void fun(char*,char*);
char ch[50];
char temp[10]={0};
int main()
{
printf("Enter string :");
scanf("%[^'\n']s",&ch);
fun(ch,temp);
}
void fun(char *ptr,char *tptr)
{
int icnt = 0;
while(*ptr!='\0')
{
if(*ptr!=' ')
{
*tptr = *ptr;
tptr++;
icnt++;
}
else if(*ptr==' ')
{
printf("In IF bcoz of space\n");
printf("%s %d\n",temp,icnt);
icnt = 0;
//temp[10] = {0}; //*
memset(temp,0,10); //*
//Tried reseting in both the above ways *
}
ptr++;
}
if(*ptr=='\0')
{
printf("%s%d\n",temp,icnt);
}
}
Output of the above program: The34
Looks like nothing is getting stored the 2nd time in the temp variable
Excepted output: The3 cake4

Answer 1

printf("%s %d\n",temp,icnt);
temp[10] = {0};
Your function takes temp as argument and accesses that global variable directly. This is not a bug up to here but it makes no sense: The function will only work if the tptr argument has a certain value. So why using an argument at all?
temp[10] = {0};
memset(temp,0,10);
Because your function overwrites the content of that array with the line *tptr = *ptr it is not neccessary to initialize the temp array at all!
Instead you only have to ensure that the last value in the array is a zero. You do this the following way:
*tptr = 0;
printf(...,temp,...);
Theoretically you could also use memset but this is not neccessary and will take more computation time.
Output of the above program: The34
Your program increments tptr (tptr++) but it never re-sets it!
Therefore the temp array has the following content:
/* Before the first printf: */ "The\0\0\0\0\0\0\0"
/* After memset: */ "\0\0\0\0\0\0\0\0\0\0"
/* Before the second printf: */ "\0\0\0cake\0\0\0"
If your input is longer than 10 characters your program may even crash because it writes to memory it is not allowed to write to.
printf will write an empty string the second time because the first character of the temp array is NUL...
Kindly correct my program if there are mistakes.
I would do the following changes:
I would use two different variables for tptr:
void fun(char *ptr,char *output)
{
char *tptr = output; /* here */
Instead of referencing temp in the function I would reference the argument which I would never modify. Before printf I would write the NUL byte to the end of the array and after printf I would reset the write pointer (tptr):
*tptr = *ptr; /* This remains tptr; does not become output */
*tptr++; /* This also */
...
*tptr = 0; /* This is new: Ensure the last byte is NUL */
printf(...,output,...); /* Not test, but output */
tptr = output; /* This is new: Reset the write pointer */
/* memset(...) - No longer needed */

Answer 2

#include<stdio.h>
#include<string.h>
void fun(char*,char*);
char ch[50];
char temp[10]={0};
int main()
{
printf("Enter string :");
scanf("%[^'\n']s",ch);
fun(ch,temp);
}
void fun(char *ptr,char *tptr)
{
int icnt = 0;
while(*ptr!='\0')
{
if(*ptr!=' ')
{
*tptr = *ptr;
tptr++;
icnt++;
}
else if(*ptr==' ')
{
printf("In IF bcoz of space\n");
printf("%s %d\n",temp,icnt);
icnt = 0;
//temp[10] = {0}; //*
memset(temp,0,10);
tptr = temp; /* The tptr was not reinitialised to point to base address */
//Tried reinitialization in both the above ways *
}
ptr++;
}
if(*ptr=='\0')
{
printf("%s%d\n",temp,icnt); /* Here you are printing from the base address.*/
}
}
The print was done from the base address of the array and the after reinitialisation the tptr was not set to point to the base address of the array. Code attached should work fine.

Answer 3

You have to add after "inct = 0;" the instruction : " tptr = temp;" because if you don't add it you will go out from the memory space of the table "temp". And you have also to add "*tptr='\0' " just before "printf("%s %d\n",temp,icnt);".