add head

head.c

@@ -0,0 +1,47 @@
+/* See LICENSE file for copyright and license details. */
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include "util.h"
+
+static void head(FILE *, const char *, long);
+
+int
+main(int argc, char *argv[])
+{
+	char *end, c;
+	long n = 10;
+	FILE *fp;
+
+	while((c = getopt(argc, argv, "n:")) != -1)
+		switch(c) {
+		case 'n':
+			n = strtol(optarg, &end, 0);
+			if(*end != '\0')
+				eprintf("%s: not a number\n", optarg);
+			break;
+		default:
+			exit(EXIT_FAILURE);
+		}
+	if(optind == argc)
+		head(stdin, "<stdin>", n);
+	else for(; optind < argc; optind++) {
+		if(!(fp = fopen(argv[optind], "r")))
+			eprintf("fopen %s:", argv[optind]);
+		head(fp, argv[optind], n);
+		fclose(fp);
+	}
+	return EXIT_SUCCESS;
+}
+
+void
+head(FILE *fp, const char *str, long n)
+{
+	char buf[BUFSIZ];
+	int i;
+
+	for(i = 0; i < n && fgets(buf, sizeof buf, fp); i++)
+		fputs(buf, stdout);
+	if(ferror(fp))
+		eprintf("%s: read error:", str);
+}