Segmentation Fault in C function -

i trying develop basic shell. shell need c function parse string. new c tried develop basic function , gives me segmentation fault error. please tell me missing.

#include<string.h> #include<stdio.h>   void parse(char *msg); int main() {     char *msg =  "this message";     parse(msg); }  void parse(char *msg){     char *mm;     mm = msg;      char *tok;     tok = strtok(mm," ");     while(tok == null){         tok = strtok(null," ");             printf("%s \n",tok);     } } 

error message (runtime)

segmentation fault (core dumped) 

thanks in advance

msg points string literal, , attempting modify it. in c, modifying string literals undefined behaviour (in practice, compilers place them in read-only memory).

to fix, turn msg array:

int main() {     char msg[] =  "this message";     parse(msg); } 

also, there couple of issues while loop:

1) condition wrong way round;
2) second strtok() call should appear after printf().

void parse(char *msg){     char *mm = msg;     char *tok = strtok(mm, " ");     while (tok) {         printf("%s \n",tok);         tok = strtok(null," ");     } }