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Need help to convert a string to an integer

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Join Date: Aug 2008

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c_ytsui

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Need help to convert a string to an integer

Aug 25th, 2008

Hi all,

I am new to C programming and need some of your help. I am trying to convert a string(ex. 25,000) to an integer. I use the atoi function to do the conversion, however, it only reads the initial portion of the string by stopping at the first non-numerical character. In my case, it stores the value of "25" rather than "25000". How do I remove the comma and convert it to an integer? Please advise, thanks in advance.

Carol

int result;

 Help with Code Tags 
 c Syntax (Toggle Plain Text) 
extract_value(char* param_name)
{
	char param[256], paramvalue[2048], *valueptr, valuestr[64];
	int result;
 
	sprintf(param, "{%s}", param_name);	
	strcpy(paramvalue, lr_eval_string(param));
 
	if((valueptr = (char*)strstr(paramvalue, ">")) != NULL)
		{
		strcpy(valuestr, &valueptr[1]);
		result = atoi(valuestr);
		}
	lr_output_message("Param: %s, Value: %d", param_name, result);
 
	return result;
}
extract_value(char* param_name)
{
	char param[256], paramvalue[2048], *valueptr, valuestr[64];
	int result;

	sprintf(param, "{%s}", param_name);	
	strcpy(paramvalue, lr_eval_string(param));

	if((valueptr = (char*)strstr(paramvalue, ">")) != NULL)
		{
		strcpy(valuestr, &valueptr[1]);
		result = atoi(valuestr);
		}
	lr_output_message("Param: %s, Value: %d", param_name, result);

	return result;
}

Last edited by Ancient Dragon; Aug 25th, 2008 at 7:35 pm. Reason: add code tags

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Re: Need help to convert a string to an integer

-1

Aug 25th, 2008

you can remove the comma by shifting all other characters left one place, assuming the string is in read/write memory.

 Help with Code Tags 
 C Syntax (Toggle Plain Text) 
char str[] = "25,000";
// locate the comma
char* ptr = strchr(str,',');
// shift remaining characters left 1 place
memmove(ptr, ptr+1, strlen(ptr+1) + 1);
char str[] = "25,000";
// locate the comma
char* ptr = strchr(str,',');
// shift remaining characters left 1 place
memmove(ptr, ptr+1, strlen(ptr+1) + 1);

Last edited by Ancient Dragon; Aug 25th, 2008 at 7:41 pm.

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Aia

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Re: Need help to convert a string to an integer

Aug 25th, 2008

>I use the atoi function to do the conversion
Take a look at strtol(), it would be better, atoi() has poor error handling

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jephthah

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Re: Need help to convert a string to an integer

Aug 26th, 2008

check this out. compile it and run it and see how it works.

the function "stripCharacters" will strip out any undesired characters using the standard library function strtok... very powerful function, learn to use it.

 Help with Code Tags 
 c Syntax (Toggle Plain Text) 
#include <stdio.h>
#include <string.h>
#define MAXLEN    32
 
//////////////////////////////////////////////////////
//
// function : stripCharacters
// 
// input  : character string to be modified
// output : the modified string (original is lost!!)
// return : number of chars stripped, or -1 if error
//
//////////////////////////////////////////////////////
int stripCharacters(char * user_str)
{
   char copy_str[MAXLEN], *ptr;
   const char CHARS_TO_STRIP[10] = ",$%#";
 
   //error check, make sure string is not too long
   int stringlen = strlen(user_str);
   if (stringlen > MAXLEN)
       return -1;
 
   //make copy of user string, modified version will replace it
   strncpy (copy_str,user_str,MAXLEN);
 
   //look for first instance of "strip characters"
   ptr = strtok(copy_str, CHARS_TO_STRIP);
   strcpy(user_str,ptr);
 
   //look for additional strip characters
   while(ptr)
   {
      ptr = strtok(NULL, CHARS_TO_STRIP);
      if (ptr)
         strcat(user_str,ptr);
   }
 
   //modified string is passed back in original string variable
   //return value indicates number of chars stripped, if any
   return (stringlen - strlen(user_str));
}
 
 
 
int main()
{
   char myString[32];
   int retVal;
 
   strcpy(myString,"1,234,567,890,123");
   printf("original:  %s\n",myString);
   retVal = stripCharacters(myString);
   printf("modified:  %s   (stripped %i)\n\n",myString,retVal);
 
   strcpy(myString,"$5,299.99");
   printf("original:  %s\n",myString);
   retVal = stripCharacters(myString);
   printf("modified:  %s   (stripped %i)\n\n",myString,retVal);
 
   strcpy(myString,"0.039%");
   printf("original:  %s\n",myString);
   retVal = stripCharacters(myString);
   printf("modified:  %s   (stripped %i)\n\n",myString,retVal);
 
   strcpy(myString,"#103");
   printf("original:  %s\n",myString);
   retVal = stripCharacters(myString);
   printf("modified:  %s   (stripped %i)\n\n",myString,retVal);
 
   strcpy(myString,"999888777");
   printf("original:  %s\n",myString);
   retVal = stripCharacters(myString);
   printf("modified:  %s   (stripped %i)\n\n",myString,retVal);
 
   strcpy(myString,"123,456,789,012,345,678,901,234,567,890");
   printf("original:  %s\n",myString);
   retVal = stripCharacters(myString);
   printf("modified:  %s   (stripped %i)\n\n",myString,retVal);
 
 
   return 0;
}
#include <stdio.h>
#include <string.h>
#define MAXLEN    32

//////////////////////////////////////////////////////
//
// function : stripCharacters
// 
// input  : character string to be modified
// output : the modified string (original is lost!!)
// return : number of chars stripped, or -1 if error
//
//////////////////////////////////////////////////////
int stripCharacters(char * user_str)
{
   char copy_str[MAXLEN], *ptr;
   const char CHARS_TO_STRIP[10] = ",$%#";
   
   //error check, make sure string is not too long
   int stringlen = strlen(user_str);
   if (stringlen > MAXLEN)
       return -1;

   //make copy of user string, modified version will replace it
   strncpy (copy_str,user_str,MAXLEN);
   
   //look for first instance of "strip characters"
   ptr = strtok(copy_str, CHARS_TO_STRIP);
   strcpy(user_str,ptr);

   //look for additional strip characters
   while(ptr)
   {
      ptr = strtok(NULL, CHARS_TO_STRIP);
      if (ptr)
         strcat(user_str,ptr);
   }
   
   //modified string is passed back in original string variable
   //return value indicates number of chars stripped, if any
   return (stringlen - strlen(user_str));
}



int main()
{
   char myString[32];
   int retVal;

   strcpy(myString,"1,234,567,890,123");
   printf("original:  %s\n",myString);
   retVal = stripCharacters(myString);
   printf("modified:  %s   (stripped %i)\n\n",myString,retVal);

   strcpy(myString,"$5,299.99");
   printf("original:  %s\n",myString);
   retVal = stripCharacters(myString);
   printf("modified:  %s   (stripped %i)\n\n",myString,retVal);

   strcpy(myString,"0.039%");
   printf("original:  %s\n",myString);
   retVal = stripCharacters(myString);
   printf("modified:  %s   (stripped %i)\n\n",myString,retVal);

   strcpy(myString,"#103");
   printf("original:  %s\n",myString);
   retVal = stripCharacters(myString);
   printf("modified:  %s   (stripped %i)\n\n",myString,retVal);

   strcpy(myString,"999888777");
   printf("original:  %s\n",myString);
   retVal = stripCharacters(myString);
   printf("modified:  %s   (stripped %i)\n\n",myString,retVal);

   strcpy(myString,"123,456,789,012,345,678,901,234,567,890");
   printf("original:  %s\n",myString);
   retVal = stripCharacters(myString);
   printf("modified:  %s   (stripped %i)\n\n",myString,retVal);


   return 0;
}