Thread: Replacing a part of a string with an other???

Hey all,

I have a string1: "This is the string"
and I want to replace the word "the" with string2: "not a"
so that string1 becomes "This is not a string"

i know how to use strstr to find the word i want to replace, but i don't know how to actually replace the word with the other string.

How do i do this?

Thanks

Do you like that?

Code:

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

char *ReplaceStrInsideString(char *ptrStr, const char *replaceStr, const char *insertStr)
{
	if(!ptrStr || !insertStr)
	{
		fprintf(stderr,"NULL input strings.\n");
		return NULL;
	}
	else
	{
		char *nptr = NULL;
		if((nptr = strstr(ptrStr, replaceStr)) == NULL)
		{
			fprintf(stderr, "Can not find \"%s\" string inside \"%s\ string.\n", replaceStr, ptrStr);
			return NULL;
		}
		else
		{
			/* Compute final length. */
			int nEndLen, nReplaceStartIndex;
			/* Save the lengths that are needed. */
			int nInsertLen = strlen(insertStr);
			int nReplaceLen = strlen(replaceStr);
			int nInitLen = strlen(ptrStr);
			/* Final length of the string is known. */
			int nFinalLen = nInitLen - nReplaceLen + nInsertLen + 1;
			/* Pointers to strings. */
			char *nFinalStr = NULL;
			char *nEndStr = NULL;
			if((nFinalStr = calloc(nFinalLen, sizeof(char))) == NULL)
			{
				fprintf(stderr, "Memory Allocation Error.\n");
				return NULL;
			}
			/* Where is the replace string? */
			nReplaceStartIndex = nptr - ptrStr;
			if(nReplaceStartIndex < 0)
				nReplaceStartIndex = -nReplaceStartIndex;
			nEndLen = nInitLen - nReplaceStartIndex + nReplaceLen+1;
			if((nEndStr = calloc(nEndLen, sizeof(char))) == NULL)
			{
				fprintf(stderr, "Memory Allocation Error.\n");
				return NULL;
			}
			/* Hold the remaining part. */
			strcpy(nEndStr, &ptrStr[nReplaceStartIndex+nReplaceLen]);
			/* Copy characters untill the replace string. */
			strncpy(nFinalStr, ptrStr, nReplaceStartIndex);
			/* Copy now the insertStr. */
			strncpy(&nFinalStr[nReplaceStartIndex], insertStr, nInsertLen);
			/* Append the final characters. */
			strcpy(&nFinalStr[nReplaceStartIndex+nInsertLen], nEndStr); 
			/* Free what is unused. */
			free(nEndStr);
			/* Return the str. */
			return nFinalStr;
		}
	}
}

/* Main. */
int main(int argc, char *argv[])
{
	char *nInitString = "This is the string.";
	char *nFinalStr = ReplaceStrInsideString(nInitString, "the", "is not");
	printf("Initial String :\t%s\nString Replaced:\t%s\n\n",nInitString, nFinalStr);
	printf("Hit enter to continue....");
	getchar();
}

Printed Results:

Initial String : This is the string.
String Replaced: This is is not string.

Hit enter to continue....

(Well memmove can be usefull here......xmmmmmmmmmmmmm)

Sure there is a memory leak as i am not freeing the memory used, OS can handle it properly but ok you are right. Secondly about the comments this is C commenting and it is my way of writing so i dont bother. Thirdly yes you can not use the nEndStr and this can be easily avoided and this is the only thing i agree with. But if you want to put yourself cleverer write down your own code and i will comment it too. What i ve done is to provide the user with an answer so to have a point in C how to do it. You are far better....

Thank C programmers...

Give me your good practice......

Bad practices.....
XAXAXAXA!!!!!

Bad practice beacause i got a bit more memory for the nEndStr haaa?

OK, give me a break dude, God of C....