bore

commit 0d57993ee0e988c75bcefe8c8f3630932c12b366
parent 13b4d6138c5be4da13e29ef62b0dfa8dc6b9566d
Author: phoebos <ben@bvnf.space>
Date:   Mon,  4 Oct 2021 19:49:39 +0100

head: add

Diffstat:
M
Makefile
 | 
1
+
M
PROGRESS
 | 
2
+-
A
head.c
 | 
83
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

3 files changed, 85 insertions(+), 1 deletion(-)
diff --git a/Makefile b/Makefile
@@ -5,6 +5,7 @@ BINS = \
 	echo \
 	ed \
 	false \
+	head \
 	ls \
 	mkdir \
 	tee \
diff --git a/PROGRESS b/PROGRESS
@@ -18,7 +18,7 @@
 [x] false
 [ ] find
 [ ] grep
-[ ] head
+[x] head [-n]
 [ ] id
 [ ] kill
 [ ] ln
diff --git a/head.c b/head.c
@@ -0,0 +1,83 @@
+#include <errno.h>
+#include <limits.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+int
+head(FILE *f, int n) {
+    int i;
+    size_t len = LINE_MAX;
+    char *buf = malloc(len);
+    if (buf == NULL) {
+        fprintf(stderr, "head: %s\n", strerror(errno));
+        return 1;
+    }
+    for (i = 0; i < n; i++) {
+        if (getline(&buf, &len, f) == -1) {
+            if (ferror(f)) {
+                fprintf(stderr, "head: %s\n", strerror(errno));
+                return 1;
+            }
+            if (feof(f))
+                break;
+        }
+        printf(buf);
+    }
+
+    return 0;
+}
+
+int
+main(int argc, char **argv) {
+    int n = 10;
+    int ret = 0;
+
+    int c;
+    while ((c = getopt(argc, argv, ":n:")) != -1) {
+        switch (c) {
+            case 'n':
+                n = atoi(optarg);
+                if (n <= 0) {
+                    fprintf(stderr, "head: invalid number '%s'\n", optarg);
+                    return 1;
+                }
+                break;
+            case ':':
+            case '?':
+                fprintf(stderr, "usage: %s [-n num] [file...]\n", *argv);
+                return 1;
+        }
+    }
+
+    argc -= optind;
+    argv += optind - 1;
+
+
+    if (argc == 0)
+        return head(stdin, n);
+
+    FILE *f;
+    while (*++argv) {
+        if (**argv == '-' && *(*argv + 1) == '\0')
+            f = stdin;
+        else {
+            f = fopen(*argv, "r");
+            if (f == NULL) {
+                fprintf(stderr, "head: %s: %s\n", *argv, strerror(errno));
+                ret = 1;
+                continue;
+            }
+        }
+        if (head(f, n) != 0)
+            ret = 1;
+
+        if (f != stdin && fclose(f) == EOF) {
+            fprintf(stderr, "head: %s: %s\n", *argv, strerror(errno));
+            ret = 1;
+            continue;
+        }
+    }
+    return ret;
+}