1) Alter the program such that only the correct output is sent to the standard output stream (stdout), while error and help messages are sent to the standard error stream (stderr). (Hint: use fprintf.)

2) Implement an optional command-line switch '-fFILENAME' that sends program output to a file named FILENAME (i.e., filename specified as a command line argument).

3) Add support for matching arbitrary numbers of words, not just 5. (Hint: use malloc, and don't worry too much about memory efficiency).

4) Safeguard the program from buffer overflow attacks. (Hint: 'gets' is BAD. Use fgets instead, which specifies the maximum number of characters to be read in.)

5) Allow multiple words to be specified per line. (Hint 1: Understand 'strtok'. Hint 2: Be careful about the newline character ' ' at the end of the line.)

/* About this program: - This program counts words. - The specific words that will be counted are passed in as command-line arguments. - The program reads words (one word per line) from standard input until EOF or an input line starting with a dot '.' - The program prints out a summary of the number of times each word has appeared. - Various command-line options alter the behavior of the program. E.g., count the number of times 'cat', 'nap' or 'dog' appears. > ./main cat nap dog Given input: cat . Expected output: Looking for 3 words Result: cat:1 nap:0 dog:0 */ #include #include

#include #include "smp0_tests.h" #define LENGTH(s) (sizeof(s) / sizeof(*s)) /* Structures */ typedef struct { char *word; int counter; } WordCountEntry; int process_stream(WordCountEntry entries[], int entry_count) { short line_count = 0; char buffer[30]; while (gets(buffer)) { if (*buffer == '.') break; /* Compare against each entry */ int i = 0; while (i < entry_count) { if (!strcmp(entries[i].word, buffer)) entries[i].counter++; i++; } line_count++; } return line_count; } void print_result(WordCountEntry entries[], int entry_count) { int i = 0;

printf("Result: "); while (i < entry_count) { printf("%s:%d ", entries[i].word, entries[i].counter); i++; } } void printHelp(const char *name) { printf("usage: %s [-h] ... ", name); } int main(int argc, char **argv) { const char *prog_name = *argv; WordCountEntry entries[5]; int entryCount = 0; /* Entry point for the testrunner program */ if (argc > 1 && !strcmp(argv[1], "-test")) { run_smp0_tests(argc - 1, argv + 1); return EXIT_SUCCESS; }

argv++; while (*argv != NULL) { if (**argv == '-') { switch ((*argv)[1]) { case 'h': printHelp(prog_name); break; default: printf("%s: Invalid option %s. Use -h for help. ", prog_name, *argv); } } else{ if (entryCount < LENGTH(entries)) { entries[entryCount].word = *argv; entries[entryCount++].counter = 0; } } argv++; } // end while if (entryCount == 0) { printf("%s: Please supply at least one word. Use -h for help. ", prog_name); return EXIT_FAILURE; } if (entryCount == 1) { printf("Looking for a single word "); } else { printf("Looking for %d words ", entryCount); } process_stream(entries, entryCount); print_result(entries, entryCount); return EXIT_SUCCESS; }