CODEWITHSUNDEEP
cstring
user2525288
user2525288

Reputation: 87

Issues with string processing in C

I'm stuck on a HW assignment where I'm required to write a program that transforms a bunch of English words (in a list separated by new lines in a input .txt file) into a bunch of Pig Latin words (into a list separated by new lines in an output .txt file). I've gotten really close, but the strncat function (string concatentation) function that I'm using is somehow throwing in a new line, which really throws off the text that I'm printing to the stdout (using it to test for now). Any ideas why this might be happening? Here is my code:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define MAX_STR_SIZE 100

char * convertToPigLatin (char * strPtr, char * pLatinStr);

int main(int argc, char *argv[])
{
   char str[MAX_STR_SIZE];
   char pStr[MAX_STR_SIZE];
   //char *pStrPtr; 
   FILE *fileInPtr;                                     //Create file name
   FILE *fileOutPtr;    

   fileInPtr = fopen("pigLatinIn.txt", "r");    //Assign text to file
   fileOutPtr = fopen("pigLatinOut.txt", "w");

   //pStrPtr = pStr; 

   if(fileInPtr == NULL)                                //Check if file exists
   {
      printf("Failed");
      exit(-1); 
   }


   do                   //Cycles until end of text
   {
      fgets(str, 29, fileInPtr);                //Assigns word to *char

      str[29] = '\0';                           //Optional: Whole line

      convertToPigLatin(str, pStr); 
      fprintf(fileOutPtr, "%s", pStr); 

   }  while(!feof(fileInPtr));   

   system("pause"); 
}

char * convertToPigLatin (const char * strPtr, char * pStrPtr)
{
   int VowelDetect = 0; 
   int LoopCounter = 0; 
   int consonantCounter = 0; 
   char pStr[MAX_STR_SIZE] = {'\0'};
   char cStr[MAX_STR_SIZE] = {'\0'};
   char dStr[] = {'-','\0'}; 
   char ayStr[] = {'a','y','\0'};
   char wayStr[] = {'w','a','y','\0'};

   pStrPtr = pStr; 

   while (*strPtr != '\0')
   {
      if (*strPtr == 'a' || *strPtr == 'e' || *strPtr == 'i' || *strPtr == 'o' || *strPtr == 'u' || VowelDetect ==1)
      {
         strncat(pStr, strPtr, 1); 
         VowelDetect = 1; 
      }
      else
      {
         strncat(cStr, strPtr, 1); 
         consonantCounter++; 
      }
      *strPtr++;
   }
   strcat(pStr, dStr); 
   if (consonantCounter == 0)  
   {
      strcat(pStr, wayStr);
   }
   else
   {
      strcat(pStr, cStr);
      strcat(pStr, ayStr);
   }  
   printf("%s", pStr);                       

 //  return pStrPtr; 
}

Upvotes: 1

Views: 391

Answers (3)

Lidong Guo
Lidong Guo

Reputation: 2857

@selbie is right ,

*strPtr++;

==>

++strPtr;

also add this before call convertToPigLatin

if(str[0] == '\0')
        break;

And it works,the pigLatinOut.txt show work in Latin,but all in one line!

like this : (I know nothing about Latin,is that waht you want?):

pigLatinIn.txt

hello world!
I am line one!
I am line two!
I am line three!

pigLatinOut.txt 

𬌿\q·ð¬Œ¿\q·ð¬Œ¿\q·ð¬Œ¿\q·

Upvotes: 0

Nigel
Nigel

Reputation: 354

There are a variety of oddities in this code, but the problem you're asking about is created by your while loop in convertToPigLatin. You loop while *strPtr != '\0', and \n is certainly not \0, so you are adding that to pStr.

Now for the rest of the code, just a few comments:

  • Using strncat to copy one character is odd usage. Typically, one would use simple character assignment instead (as in str1[i] = str2[j])
  • *strPtr++ is incrementing the pointer and dereferencing it, but then doing nothing with the dereferenced value. You just want strPtr++ there.
  • You can create a string literal using char str[] = "some string". You don't need to use array initialization syntax.

Those are the ones that jumped out at me without a detailed reading. Good luck on your future assignments.

Edit to add that stepping through your code with a debugger is very valuable in these cases. You would see exactly where the newline is being added.

Upvotes: 2

Jongware
Jongware

Reputation: 22478

The problem lies not in strncat, but in your input:

fgets(str, 29, fileInPtr);                //Assigns word to *char
str[29] = '\0';                           //Optional: Whole line

If you enter something other than 29 characters, the hard return is not overwritten. Use this instead:

str[strlen(str)-1] = 0;

.. actually, this will always overwrite the 29th character, even if it isn't a hard return (when you entered more than 29 characters). So a better solution would be

char *ptr = strchr(str, '\n');
if (ptr) *ptr = 0;

You cannot use MAX_STR_SIZE for this either (which you defined-but didn't use in your code), since fgets

[r]eads characters from stream and stores them as a C string into str until (num-1) characters have been read or either a newline or the end-of-file is reached, whichever happens first. (http://www.cplusplus.com/reference/cstdio/fgets/)

-- the last character could be the terminating zero, or a hard return.

Upvotes: 1

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