GMS Linux: start?

userprog/cat/Makefile

@@ -0,0 +1,15 @@
+TARGET = cat
+SRCS = cat.c
+CC = gcc
+CFLAGS = -static -Wall
+
+OUT_BIN ?= $(TARGET)
+
+all: $(OUT_BIN)
+
+$(OUT_BIN): $(SRCS)
+	@echo "   [CC] Compiling to $(OUT_BIN)..."
+	$(CC) $(CFLAGS) -o $@ $^
+
+clean:
+	rm -f $(TARGET)

userprog/cat/cat.c

@@ -0,0 +1,30 @@
+#include <stdio.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+int main(int argc, char *argv[]) {
+    char buf[1024];
+    int n;
+    int fd;
+
+    if (argc == 1) {
+        while ((n = read(STDIN_FILENO, buf, sizeof(buf))) > 0) {
+            write(STDOUT_FILENO, buf, n);
+        }
+        return 0;
+    }
+
+    for (int i = 1; i < argc; i++) {
+        fd = open(argv[i], O_RDONLY);
+        if (fd < 0) {
+            perror(argv[i]);
+            continue;
+        }
+
+        while ((n = read(fd, buf, sizeof(buf))) > 0) {
+            write(STDOUT_FILENO, buf, n);
+        }
+        close(fd);
+    }
+    return 0;
+}