c - static variable scope inside and outside the function -

please notice static variable selection. testing if selection assigned correct char string within different scope.

#include <stdio.h> #include <stdlib.h> #include <string.h>  static char* selection;  static char* sel_item(char* text) {     char* pch;     char buf[80];     strcpy(buf, text);     pch = strtok(buf, " ");     return pch; }  static int display_ecnt_codes(char* text) {        char buf[80];     strcpy(buf, text);      selection = sel_item(buf);     // why if output selection here, selection random char, not correct char "srfpro".     // printf("display_ecnt_codes: %s\n", selection);  }  int acode_prockey() {     char text[] = "srfpro - surface protection (dealerproduct)";     display_ecnt_codes(text);      // why if output selection here, prints correct char string "srfpro".     // what's difference between scope , above scope?     printf("acode_prockey: %s\n", selection);  }  int main () {     acode_prockey();     // output srfpro, first token of char text[].     printf("main: %s\n", selection);   }    

i hoping can explain global static varible "selection". when printf inside function "display_ecnt_codes", outputs random char. if not printf inside function, output correct char in main function.

in following function, returning pointer not valid after function returns.

static char* sel_item(char* text) {     char* pch;      // array on stack     char buf[80];     strcpy(buf, text);      // pointer element of array.     pch = strtok(buf, " ");      // returns pointer not valid after function returns.     return pch; } 

later on, use invalid pointer stored in selection. program exhibits undefined behavior because of that.