k9core

commit 25063680dc66013d98d541104f0d50c4967c18dc
parent bfd05a231834e67d6bf0732c287769c7c8231569
Author: aabacchus <ben@bvnf.space>
Date:   Tue, 14 Sep 2021 19:05:23 +0100

head: rewrite using getopt and open, read rather than fopen,fgetc

Diffstat:
M
src/head.c
 | 
61
++++++++++++++++++++++++++++++++++++++-----------------------

1 file changed, 38 insertions(+), 23 deletions(-)
diff --git a/src/head.c b/src/head.c
@@ -1,27 +1,31 @@
 #include <errno.h>
+#include <fcntl.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <sys/stat.h>
+#include <unistd.h>
 
 int
-head(FILE *file, int lines)
+head(int fd, int lines)
 {
-	if(file == NULL) {
-		fprintf(stderr, "head: %s\n", strerror(errno));
-		return 1;
-	}
 	int a;
+	ssize_t r;
 	int c = 0;
 
-	while((a = fgetc(file)) != EOF) {
-		if(a == '\n')
+	while((r = read(fd, &a, 1)) > 0) {
+		if(r == -1) {
+			fprintf(stderr, "head: %s\n", strerror(errno));
+			return 1;
+		}
+		if((char)a == '\n')
 			++c;
 
 		putchar(a);
 		if(c == lines)
-			return lines;
+			break;
 	}
-	return lines;
+	return 0;
 }
 
 int
@@ -29,21 +33,32 @@ main(int argc, char *argv[])
 {
 	int lines = 10;
 	int return_value = 0;
-	switch(argc) {
-		case 1:
-			return_value = head(stdin, lines);
-			break;
-		case 2:
-			return_value = head(fopen(argv[1], "r"), lines);
-			break;
-		case 3:
-			lines = abs(atoi(argv[1]));
-			return_value = head(fopen(argv[2], "r"), lines);
-			break;
-		default:
-			lines = atoi(argv[2]);
-			return_value = head(fopen(argv[3], "r"), lines);
+	int c, fd;
+	c = getopt(argc, argv, "n:");
+	switch(c) {
+		case 'n':
+			lines = atoi(optarg);
+			if(lines == 0) {
+				fprintf(stderr, "head: invalid number '%s'\n", optarg);
+				return 1;
+			}
 			break;
+		case ':':
+		case '?':
+			fprintf(stderr, "usage: head [-n N] file\n");
+			return 1;
+	}
+
+	if(optind == argc)
+		fd = 0;
+	else {
+		fd = open(argv[optind], O_RDONLY);
+		if(fd == -1) {
+			fprintf(stderr, "head: %s: %s\n", argv[optind], strerror(errno));
+			return 1;
+		}
 	}
+	return_value = head(fd, lines);
+	close(fd);
 	return return_value;
 }