Add TIOCGWINSZ ioctl so userland can determine terminal geometry.

(Don't) use this to implement short-form output in ls.
I'm too tired to make a nice column formatting algorithm.
I just wanted something concise when I type "ls".

Userland/ls.cpp

@@ -1,17 +1,97 @@
-#include <LibC/stdio.h>
-#include <LibC/unistd.h>
-#include <LibC/dirent.h>
-#include <LibC/errno.h>
-#include <LibC/string.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <dirent.h>
+#include <errno.h>
+#include <string.h>
+#include <getopt.h>
+#include <sys/ioctl.h>
+#include <AK/String.h>
+#include <AK/Vector.h>
 
 static int do_dir(const char* path);
+static int do_dir_short(const char* path);
+
+static bool flag_colorize = true;
+static bool flag_long = false;
+static bool flag_show_dotfiles = false;
 
 int main(int argc, char** argv)
 {
-    if (argc == 2) {
-        return do_dir(argv[1]);
+    int opt;
+    while ((opt = getopt(argc, argv, "laG")) != -1) {
+        switch (opt) {
+        case 'a':
+            flag_show_dotfiles = true;
+            break;
+        case 'l':
+            flag_long = true;
+            break;
+        case 'G':
+            flag_colorize = false;
+            break;
+        default:
+            fprintf(stderr, "usage: ls [-lvG] [path]\n");
+            return 1;
+        }
     }
-    return do_dir(".");
+
+    const char* path;
+
+    if (optind >= argc)
+        path = ".";
+    else
+        path = argv[optind];
+
+    if (flag_long)
+        return do_dir(path);
+    return do_dir_short(path);
+}
+
+void get_geometry(unsigned& rows, unsigned& columns)
+{
+    struct winsize ws;
+    ioctl(0, TIOCGWINSZ, &ws);
+    rows = ws.ws_row;
+    columns = ws.ws_col;
+}
+
+int print_name(struct stat& st, const char* name, const char* path_for_link_resolution = nullptr)
+{
+    int nprinted = strlen(name);
+    if (!flag_colorize) {
+        printf("%s", name);
+    } else {
+        const char* begin_color = "";
+        const char* end_color = "\033[0m";
+
+        if (S_ISLNK(st.st_mode))
+            begin_color = "\033[36;1m";
+        else if (S_ISDIR(st.st_mode))
+            begin_color = "\033[34;1m";
+        else if (st.st_mode & 0111)
+            begin_color = "\033[32;1m";
+        else if (S_ISCHR(st.st_mode) || S_ISBLK(st.st_mode))
+            begin_color = "\033[33;1m";
+        printf("%s%s%s", begin_color, name, end_color);
+    }
+    if (S_ISLNK(st.st_mode)) {
+        if (path_for_link_resolution) {
+            char linkbuf[256];
+            ssize_t nread = readlink(path_for_link_resolution, linkbuf, sizeof(linkbuf));
+            if (nread < 0) {
+                perror("readlink failed");
+            } else {
+                nprinted += printf(" -> %s", linkbuf);
+            }
+        } else {
+            nprinted += printf("@");
+        }
+    } else if (S_ISDIR(st.st_mode)) {
+        nprinted += printf("/");
+    } else if (st.st_mode & 0111) {
+        nprinted += printf("*");
+    }
+    return nprinted;
 }
 
 int do_dir(const char* path)
@@ -21,9 +101,11 @@ int do_dir(const char* path)
         perror("opendir");
         return 1;
     }
-    bool colorize = true;
     char pathbuf[256];
+
     while (auto* de = readdir(dirp)) {
+        if (de->d_name[0] == '.' && !flag_show_dotfiles)
+            continue;
         sprintf(pathbuf, "%s/%s", path, de->d_name);
 
         struct stat st;
@@ -70,37 +152,63 @@ int do_dir(const char* path)
 
         printf(" %10u  ", st.st_size);
 
-        const char* beginColor = "";
-        const char* endColor = "";
+        print_name(st, de->d_name, pathbuf);
 
-        if (colorize) {
-            if (S_ISLNK(st.st_mode))
-                beginColor = "\033[36;1m";
-            else if (S_ISDIR(st.st_mode))
-                beginColor = "\033[34;1m";
-            else if (st.st_mode & 0111)
-                beginColor = "\033[32;1m";
-            else if (S_ISCHR(st.st_mode) || S_ISBLK(st.st_mode))
-                beginColor = "\033[33;1m";
-            endColor = "\033[0m";
-        }
-
-        printf("%s%s%s", beginColor, de->d_name, endColor);
-
-        if (S_ISLNK(st.st_mode)) {
-            char linkbuf[256];
-            ssize_t nread = readlink(pathbuf, linkbuf, sizeof(linkbuf));
-            if (nread < 0) {
-                perror("readlink failed");
-            } else {
-                printf(" -> %s", linkbuf);
-            }
-        } else if (S_ISDIR(st.st_mode)) {
-            printf("/");
-        } else if (st.st_mode & 0111) {
-            printf("*");
-        }
         printf("\n");
     }
+    closedir(dirp);
+    return 0;
+}
+
+int do_dir_short(const char* path)
+{
+    unsigned rows;
+    unsigned columns;
+    get_geometry(rows, columns);
+
+    DIR* dirp = opendir(path);
+    if (!dirp) {
+        perror("opendir");
+        return 1;
+    }
+
+    Vector<String> names;
+    size_t longest_name = 0;
+    while (auto* de = readdir(dirp)) {
+        if (de->d_name[0] == '.' && !flag_show_dotfiles)
+            continue;
+        names.append(de->d_name);
+        if (names.last().length() > longest_name)
+            longest_name = names.last().length();
+    }
+    closedir(dirp);
+
+    int printed_on_row = 0;
+
+    for (size_t i = 0; i < names.size(); ++i) {
+        auto& name = names[i];
+        struct stat st;
+        char pathbuf[256];
+        sprintf(pathbuf, "%s/%s", path, name.characters());
+        int rc = lstat(pathbuf, &st);
+        if (rc == -1) {
+            printf("lstat(%s) failed: %s\n", pathbuf, strerror(errno));
+            return 2;
+        }
+
+        unsigned nprinted = print_name(st, name.characters());
+        unsigned column_width = 14;
+        printed_on_row += column_width;
+
+        for (unsigned i = nprinted; i < column_width; ++i)
+            printf(" ");
+        if ((printed_on_row + column_width) >= columns) {
+            if (i != names.size() - 1)
+                printf("\n");
+            printed_on_row = 0;
+        }
+    }
+    printf("\n");
+
     return 0;
 }