twordcount2.c

unix linux 编程实践源代码

/* twordcount2.c - threaded word counter for two files.	   */
/*                 version 2: uses mutex to lock counter   */

#include  <stdio.h>
#include  <pthread.h>
#include  <ctype.h>

int	        total_words ;    /* the counter and its lock */
pthread_mutex_t counter_lock = PTHREAD_MUTEX_INITIALIZER;

main(int ac, char *av[])
{
	pthread_t t1, t2;		/* two threads */
	void	  *count_words(void *);

	if ( ac != 3 ){
		printf("usage: %s file1 file2\n", av[0]);
		exit(1);
	}
	total_words = 0;
	pthread_create(&t1, NULL, count_words, (void *) av[1]);
	pthread_create(&t2, NULL, count_words, (void *) av[2]);
	pthread_join(t1, NULL);
	pthread_join(t2, NULL);
	printf("%5d: total words\n", total_words);
}
void *count_words(void *f)
{
	char *filename = (char *) f;
	FILE *fp;
	int  c, prevc = '\0';
	
	if ( (fp = fopen(filename, "r")) != NULL ){
		while( ( c = getc(fp)) != EOF ){
			if ( !isalnum(c) && isalnum(prevc) ){
				pthread_mutex_lock(&counter_lock);
				total_words++;
				pthread_mutex_unlock(&counter_lock);
			}
			prevc = c;
		}
		fclose(fp);
	} else 
		perror(filename);
	return NULL;
}