c - Why is one seg faulting and the other not? -

hi have program needs compare string array predefined string when use variable args[0] works in function strcmp below

int gash_execute(char **args){     int i;      if(args[0] == null){         return 1;     }      for(i = 0; < gash_command_num(); i++){         if(strcmp(args[0], functions[i]) == 0){             return(*function_address[i])(args);              }      }     return gash_launch(args); } 

however when trying strcmp args[i] such below seg fault. can me find solution problem?

int gash_execute(char **args){     int i;      if(args[0] == null){         return 1;     }      for(i = 0; < gash_command_num(); i++){         if(strcmp(args[i], functions[i]) == 0){             return(*function_address[i])(args);              }      }     return gash_launch(args); } 

args[] array of strings separated spaces, program custom shell, pretend in shell command line input "cat echo ls" args[0] "cat" , on. need implement i/o redirection. need check every element of args check if represent symbols "<" ">" "|" , if 1 of them can take there

without seeing code, or report tool such valgrind, can't sure. can tell loop full of potential problems.

for(i = 0; < gash_command_num(); i++){     if(strcmp(args[i], functions[i]) == 0){         return(*function_address[i])(args);          }  } 

it's iterating through 3 arrays (args, functions, , function_address) based on function call takes none of variables (gash_command_num()) has unknown relation how many elements in arrays.

and it's using 2 global variables (functions , function_addresses) contain anything.

if things related, suggest making explicit... suspect they're not. suspect loop logic wrong. it's comparing args[i] functions[i]. suspect gash_command_num() size of functions , loop walking off args.

what suspect want see if args[0] matches function name in functions , call related function. if args[0] ls want check if there's built in shell function ls , call arguments.

rather searching list on , on again, , having manage 2 parallel lists, better served hash table. keys function names, values function pointers. c doesn't have hash table built in, there's plenty of libraries that. gnome lib solid choice , many other basic functionality c missing.

using hash table, , eliminating globals, code reduces this:

/* encapsulation */ typedef int(*shell_function_t)(char **);  int gash_execute(char **args, ghashtable *shell_functions){     int i;      if(args[0] == null){         return 1;     }      shell_function_t func = g_hash_table_lookup(shell_functions, args[0]);     if( func ) {         return(*func)(args);     }     else {         return gash_launch(args);     } } 

scanning pipes separate problem. do want loop through args looking special characters. made simpler if, when create args, ensure ends null pointer.

for(int = 0; args[i] != null; i++) {     ...check if args[i] special... }