diff --git a/ts/ts.c b/ts/ts.c
index 68c0940..f7b55ed 100644
--- a/ts/ts.c
+++ b/ts/ts.c
@@ -3,11 +3,13 @@
 #include <sys/time.h>
 #include <time.h>
 #include <unistd.h>
+#include <string.h>
+#include <errno.h>
 
 static char *cmnd;
 
 static void usage(void) {
-    fprintf(stderr, "Usage: %s [-u]\n", cmnd);
+    fprintf(stderr, "Usage: %s [-u] [-o file]\n", cmnd);
     exit(1);
 }
 
@@ -16,36 +18,64 @@ int main(int argc, char **argv) {
     int c;
     int use_microseconds = 0;
     int print_ts = 1;
+    char lastfile[FILENAME_MAX] = "", file[FILENAME_MAX] = "";
+    char *filepat = NULL;
+    FILE *fp = NULL;
 
     cmnd = argv[0];
 
-    setlinebuf(stdout);
-    while ((c = getopt(argc, argv, "u")) != EOF) {
+    while ((c = getopt(argc, argv, "uo:")) != EOF) {
 	switch (c) {
 	    case 'u':
 		use_microseconds = 1;
 		break;
+	    case 'o':
+		filepat = optarg;
+		break;
 	    default:
 		usage();
 	}
     }
+    if (!filepat) {
+	fp = stdout;
+	setlinebuf(fp);
+    }
     while ((c = getchar()) != EOF) {
 	if (print_ts) {
 	    struct timeval tv;
 	    char s[sizeof("yyyy-mm-ddThh:mm:ss")];
 	    gettimeofday(&tv, NULL);
+	    if (filepat) {
+		strftime(file, sizeof(file), filepat,
+			 localtime(&tv.tv_sec));
+		if (strcmp(lastfile, file) != 0) {
+		    if (fp) {
+			if (fclose(fp) == EOF) {
+			    fprintf(stderr, "%s: cannot close %s: %s\n", argv[0], lastfile, strerror(errno));
+			    exit(1);
+			}
+		    }
+		    if ((fp = fopen(file, "w")) == NULL) {
+			fprintf(stderr, "%s: cannot open %s: %s\n", argv[0], file, strerror(errno));
+			exit(1);
+		    }
+		    setlinebuf(fp);
+		    strcpy(lastfile, file);
+		}
+	    }
+
 	    strftime(s, sizeof(s), "%Y-%m-%dT%H:%M:%S",
 		     localtime(&tv.tv_sec));
-	    fputs(s, stdout);
+	    fputs(s, fp);
 	    if (use_microseconds) {
-		printf(".%06ld ", (long)tv.tv_usec);
+		fprintf(fp, ".%06ld ", (long)tv.tv_usec);
 	    }
-	    putchar(' ');
+	    putc(' ', fp);
 	    print_ts = 0;
 	}
-	putchar(c);
+	putc(c, fp);
 	if (c == '\n') print_ts = 1;
     }
-    if (!print_ts) putchar('\n');	// force newline at end of output
+    if (!print_ts) putc('\n', fp);	// force newline at end of output
     return 0;
 }