Why is my Bitmap returning null?

Using strstr in Unix is returning NULL and I don't know why.?

• I'm creating a shell and I have a character that is a list of allowable commands for the the shell. However, when I use strstr to check the list it returns null every time. I can't figure out why. Any suggestions? Thanks! #include <stdio.h> #include <unistd.h> #include <string.h> #include <stdlib.h> int MAX = 256; int CMD_MAX = 10; char *valid_cmds = "ls pd cd"; /* THE LIST /* void handle_signal(int signo) { printf("\n[MY_SHELL ] "); fflush(stdout); } int main() { char line_input[MAX], the_cmd[CMD_MAX]; char *new_args[CMD_MAX], *cp; int i; char c = '\0'; signal(SIGINT, SIG_IGN); signal(SIGINT, handle_signal); printf("[MY_SHELL ] "); while(c != EOF) { c = getchar(); if(c == '\n') { printf("[MY_SHELL ] "); } if (fgets(line_input, 256, stdin) != NULL) { cp = line_input; i = 0; if ((new_args[i] = strtok(cp," ")) != NULL) { sprintf(the_cmd, "%s ", new_args[i]); if(strstr(valid_cmds, the_cmd) == NULL) { printf("It's null\n"); } else { printf("It's not null\n"); } char substring = (strstr(valid_cmds, the_cmd) - valid_cmds)%3; /* OFFICIAL USE OF STRSTR */ if (substring == 0) { do { i++; cp = NULL; new_args[i] = strtok(cp, " "); } while(i < CMD_MAX - 1 && new_args[i] != NULL); new_args[i] = NULL; switch(fork()) { case 0: execvp(new_args[0], new_args); perror("exec failure "); exit(1); case -1: wait(NULL); default: int exit_pid = wait(0); } } else printf("huh?"); } } } return(0); }

• Answer:

  Not sure, but maybe it's because the_cmd must be a const char*?