Return char string from a function

Question

Im fairly new to coding in C and currently im trying to create a function that returns a c string char array and assigning to a variable    So far  ive observed that returning a char   is the most common solution  So i tried   char  createStr         char char1   m       char char2   y       char str 3       str 0    char1      str 1    char2      str 2      0       char  cp   str      return cp      My question is how do I use this returned char  and assign the char array it points to  to a char   variable   Ive tried  all led to noob-drowning errors     char  charP   createStr    char myStr 3     amp createStr    char  charP    createStr

User · Answer

If you want to return a char  from a function  make sure you malloc   it  Stack initialized character arrays make no sense in returning  as accessing them after returning from that function is undefined behavior   change it to  char  createStr         char char1   m       char char2   y       char  str   malloc 3   sizeof char        if str    NULL  return NULL      str 0    char1      str 1    char2      str 2      0       return str

User · Answer

Notice you re not dynamically allocating the variable  which pretty much means the data inside str  in your function  will be lost by the end of the function   You should have   char   createStr          char char1   m       char char2   y        char  str   malloc 3       str 0    char1      str 1    char2      str 2      0        return str       Then  when you call the function  the type of the variable that will receive the data must match that of the function return  So  you should have   char  returned str   createStr      It worths mentioning that the returned value must be freed to prevent memory leaks   char  returned str   createStr       doSomething      free returned str

User · Answer

char  charP   createStr      Would be correct if your function was correct  Unfortunately you are returning a pointer to a local variable in the function which means that it is a pointer to undefined data as soon as the function returns  You need to use heap allocation like malloc for the string in your function in order for the pointer you return to have any meaning  Then you need to remember to free it later

User · Answer

you can use a static array in your method  to avoid lose of your array when  your function ends    char   createStr          char char1   m       char char2   y        static char str 3         str 0    char1      str 1    char2      str 2      0        return str      Edit   As Toby Speight mentioned this approach is not thread safe  and also recalling the function leads to data overwrite that is unwanted in some applications  So you have to save the data in a buffer as soon as you return back from the function   However because it is not thread safe method  concurrent calls could still make problem in some cases  and to prevent this you have to use lock  capture it when entering the function and release it after copy is done  i prefer not to use this approach because its messy and error prone

User · Answer

Including  string h  makes things easier  An easier way to tackle your problem is     include  lt string h gt      char  createStr        static char str 20     my       return str    int main        char a 20       strcpy a createStr       this will copy the returned value of createStr   into a       printf   s  a       return 0

[c] Return char[]/string from a function

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