1 files changed, 118 insertions, 0 deletions
diff --git a/src/commands/printf.c b/src/commands/printf.c
new file mode 100644
index 0000000..7539316
--- /dev/null
+++ b/src/commands/printf.c
@@ -0,0 +1,118 @@
+#include "../command.h"
+#include <stdlib.h>
+
+static long cast_long(const char* arg) {
+    char* end;
+    long l = strtol(arg, &end, 10);
+    if (end == arg) {
+        return 0;
+    } else {
+        return l;
+    }
+}
+
+static double cast_double(const char* arg) {
+    char* end;
+    double d = strtod(arg, &end);
+    if (end == arg) {
+        return 0.0;
+    } else {
+        return d;
+    }
+}
+
+#define NUMBER(name, type, arg) \
+    long l = cast_long(arg); \
+    type* t = (type*) &l; \
+    type name = *t;
+
+static void handle_percent(char n, const char* arg) {
+    switch (n) {
+        case 'd':
+        case 'z': {
+            NUMBER(i, int, arg)
+            printf("%d", i);
+            break;
+        }
+        case 'u': {
+            NUMBER(u, unsigned int, arg);
+            printf("%u", u);
+            break;
+        }
+        case 'f': {
+            double d = cast_double(arg);
+            printf("%lf", d);
+            break;
+        }
+        case 'c': {
+            putchar(arg[0]);
+            break;
+        }
+        case 's': {
+            printf("%s", arg);
+            break;
+        }
+        default: {
+            putchar('%');
+            putchar(n);
+        }
+    }
+}
+
+static void handle_slash(char n) {
+    switch (n) {
+        case 'n':
+            putchar('\n');
+            break;
+        case 't':
+            putchar('\t');
+            break;
+        case 'v':
+            putchar('\v');
+            break;
+        case 'b':
+            putchar('\b');
+            break;
+        default:
+            putchar('\\');
+            putchar(n);
+    }
+}
+
+COMMAND(print) {
+    if (argc < 1) {
+        error("usage: printf FORMAT [ARG]...\n");
+    }
+
+    size_t index = 0;
+    int arg_index = 0;
+
+    while (true) {
+        char c = argv[0][index];
+        index++;
+
+        if (c == '\0') break;
+        if (c != '%' && c != '\\') {
+            putchar(c);
+            continue;
+        }
+
+        char n = argv[0][index];
+        index++;
+
+        char* arg = NULL;
+        if (arg_index < argc) {
+            arg = argv[arg_index + 1];
+        }
+
+        if (c == '%') {
+            handle_percent(n, arg);
+        } else {
+            handle_slash(n);
+        }
+
+        arg_index++;
+    }
+
+    return EXIT_SUCCESS;
+}