add tail

2 files changed, 91 insertions, 0 deletions

diff --git a/src/commands/cat.c b/src/commands/cat.c
index f5622e8..8e22706 100644
--- a/src/commands/cat.c
+++ b/src/commands/cat.c
@@ -1,7 +1,9 @@
 #include "../command.h"
 
 #include <ctype.h>
+#include <errno.h>
 #include <string.h>
+#include <sys/stat.h>
 
 struct Flags {
     bool number_lines;
@@ -138,6 +140,15 @@ COMMAND(cat) {
             continue;
         } else {
             files = true;
+            struct stat s;
+            if (stat(argv[i], &s) < 0) {
+                printf("error: failed to read %s: %s\n", argv[i], strerror(errno));
+                continue;
+            }
+            if (!S_ISREG(s.st_mode)) {
+                printf("error: %s is not a file\n", argv[i]);
+                continue;
+            }
             FILE* in = get_file(argv[i], "r");
             cat_file(in, flags);
             fclose(in);
diff --git a/src/commands/tail.c b/src/commands/tail.c
new file mode 100644
index 0000000..04f7f42
--- /dev/null
+++ b/src/commands/tail.c
@@ -0,0 +1,80 @@
+#include "../command.h"
+
+#include <stdio.h>
+#include <string.h>
+#include <sys/stat.h>
+
+static void tail_file(FILE* file) {
+    char* ring[10];
+    memset(ring, 0, sizeof(char*) * 10);
+
+    int ring_len[10];
+    
+    int index = 0;
+    int size = 0;
+
+    int read;
+    size_t len = 0;
+    char* line = NULL;
+    while ((read = getline(&line, &len, file)) != -1) {
+
+        if (ring[index] != NULL) free(ring[index]);
+        ring[index] = line;
+        ring_len[index] = read;
+
+        index++;
+        index %= 10;
+        if (size < 10) size++;
+
+        line = NULL;
+    }
+
+    index += 10 - size;
+    index %= 10;
+    
+    for (int i = 0; i < size; i++) {
+        fwrite(ring[index], ring_len[index], 1, stdout);
+        free(ring[index]);
+        index += 1;
+        index %= 10;
+    }
+
+    free(line);
+    fclose(file);
+}
+
+static void help() {
+    printf("Usage: tail [FILE]...\n\n");
+    printf("Print last 10 lines of FILEs (or stdin) to.\n");
+    printf("With more than one FILE, precede each with a filename header.\n");
+    exit(EXIT_SUCCESS);
+}
+
+COMMAND(tail) {
+    if (argc < 1) {
+        tail_file(stdin);
+        return EXIT_SUCCESS;
+    }
+
+    if (streql(argv[0], "--help")) help();
+
+    if (argc == 1) {
+        FILE* file = get_file(argv[0], "r");
+        tail_file(file);
+        return EXIT_SUCCESS;
+    }
+
+    for (int i = 0; i < argc; i++) {
+        FILE* file;
+        if (streql("-", argv[i])) {
+            file = stdin;
+        } else {
+            file = get_file_s(argv[i], "r");
+            if (file == NULL) continue;
+        }
+        printf("\n==> %s <==\n", argv[i]);
+        tail_file(file);
+    }
+
+    return EXIT_SUCCESS;
+}