替换字符串中的单个单词

Question

i have a null terminated and dynamically allocated string called 'text_buff' , which contain's the word "bar". i want to replace this word with another word of my choice, that can be longer or shorter than the original one.

here's my code up until now, i can't seem to figure out what am i doing wrong.

        char * toswap = "newword";
        int diff = strlen(toswap)-strlen("bar");
        int wlocation = strstr(text_buff,"bar")-text_buff;
        if (diff > 0) {
            text_buff = realloc(text_buff,strlen(text_buff)+diff);
            for (i=strlen(text_buff) ; i > wlocation+strlen("bar") -1; --i ){
                text_buff[i+diff] = text_buff[i];
            }
            for (i = 0 ; i < strlen("bar")+1; ++i){
                text_buff[wlocation+i] = toswap[i];

            }
        } else if (diff < 0){
                for (i=wlocation+diff ; i <strlen(text_buff);++i ){
                    text_buff[i]=text_buff[i-diff];
                }
                for (i = 0 ; i < strlen("bar")+1; ++i){
                    text_buff[wlocation+i] = toswap[i];
                }
}

Answer 1

You have the wrong loop condition when inserting the new word:

        for (i = 0 ; i < strlen("bar")+1; ++i){
            text_buff[wlocation+i] = toswap[i];
        }

It should be:

        for (i = 0 ; i < strlen(toswap); ++i){
            text_buff[wlocation+i] = toswap[i];
        }

Other than that you are missing error handling. If this is a school assignment you can probably manage without error handling, though.

Answer 2

You forget 1 character for the final '\\0';

text_buff = realloc(text_buff,strlen(text_buff)+diff);

It should be

text_buff = realloc(text_buff,strlen(text_buff)+diff + 1);