How to return a string by replacing with another string in c

Question

#include<stdio.h>

char str(char *s) {  
    char s1[100];
    printf("another string to replace:");
    scanf("%d",s1);  
    s=s1;  
    return s;
}

void main() {  
    char s[100],s2[100];  
    scanf("%s",s);  
    s2=str(s);  
    printf("%s",s);
}

How to return a string by replacing with another string in c??I'm unable to replace the string using functions

you'll probably want to use strcpy https://www.tutorialspoint.com/c_standard_library/c_function_strcpy.htm — John Boker, Apr 03 '18 at 16:28
one thing you need to change is char* str() you're currently saying it rturns 1 character. You also need to assign the result to a char* s2; in main() and John Boker has good advice. — kenny, Apr 03 '18 at 16:29
also, be careful with `scanf`. You might consider using `fgets` as suggested here: https://stackoverflow.com/questions/3302255/c-scanf-vs-gets-vs-fgets/3302594#3302594 — woz, Apr 03 '18 at 16:42

score 0 · Answer 1 · answered Apr 03 '18 at 16:40

What you're going to want to do is copy the values of the characters in s1 into your s variable. not just set one equal to the other. either using strcpy or looping through your characters in s1 and copying them directly to the correct locations in s.

https://www.tutorialspoint.com/c_standard_library/c_function_strcpy.htm

this works for me without using strcpy:

#include<stdio.h>

void str(char *s) {  
    char s1[100];
    printf("another string to replace:");
    scanf("%s",s1);  
    // not real safe but we know s and s1 have 100 characters.
    for(int i = 0; i < 100; i++) {
        s[i] = s1[i];
    }   
}

int main() {  
    char s[100],s2[100];  
    scanf("%s",s);  
    str(s);  
    printf("%s",s);
}

Support Ukraine · Accepted Answer · 2018-04-03T16:53:02.120

There a several things to say about your code.

You can't copy strings using =
The return type is wrong. Must be char*
The scanf format string is wrong. Use %s for strings.
You don't need an extra array in the function. Just scanf directly into s
Never do scanf("%s", ... Always put a limit to it like scanf("%99s", ...

Something like:

char* str(char *s) {  
    printf("another string to replace:");
    scanf("%99s",s);  
    return s;
}

void main() {  
    char s[100],s2[100];  
    scanf("%99s",s);    
    strcpy(s2, str(s));  
    printf("%s",s);
}

I am, however, not sure what you want the code to do. As it is now s and s2 just end as identical strings.

If you just want a function that can read a new value into s it can be done like:

void str(char *s) {  
    printf("another string to replace:");
    scanf("%99s",s);  
}

void main() {  
    char s[100];  
    scanf("%99s",s);    
    str(s);
    printf("%s",s);
}

How to return a string by replacing with another string in c

2 Answers2