Implement argc/argv support for spawned tasks.

Celebrate the new functionality with a simple /bin/cat implementation. :^)

Userland/.gitignore

@@ -1,3 +1,4 @@
+*.o
 id
 sh
 ps
@@ -8,4 +9,4 @@ date
 false
 true
 hostname
-*.o
+cat

Userland/Makefile

@@ -8,7 +8,8 @@ OBJS = \
        date.o \
        true.o \
        false.o \
-       hostname.o
+       hostname.o \
+       cat.o
 
 APPS = \
        id \
@@ -20,7 +21,8 @@ APPS = \
        date \
        true \
        false \
-       hostname
+       hostname \
+       cat
 
 ARCH_FLAGS =
 STANDARD_FLAGS = -std=c++17 -nostdinc++ -nostdlib
@@ -70,6 +72,9 @@ false: false.o
 hostname: hostname.o
 	$(LD) -o $@ $(LDFLAGS) $< ../LibC/LibC.a
 
+cat: cat.o
+	$(LD) -o $@ $(LDFLAGS) $< ../LibC/LibC.a
+
 .cpp.o:
 	@echo "CXX $<"; $(CXX) $(CXXFLAGS) -o $@ -c $<
 

Userland/cat.cpp

@@ -0,0 +1,30 @@
+#include <LibC/stdio.h>
+#include <LibC/unistd.h>
+#include <LibC/errno.h>
+#include <LibC/string.h>
+
+int main(int argc, char** argv)
+{
+    if (argc != 2) {
+        printf("usage: cat <file>\n");
+        return 1;
+    }
+    int fd = open(argv[1]);
+    if (fd == -1) {
+        printf("failed to open %s: %s\n", argv[1], strerror(errno));
+        return 1;
+    }
+    for (;;) {
+        char buf[128];
+        ssize_t nread = read(fd, buf, sizeof(buf));
+        if (nread == 0)
+            break;
+        if (nread < 0) {
+            printf("read() error: %s\n", strerror(errno));
+            return 2;
+        }
+        for (ssize_t i = 0; i < nread; ++i)
+            putchar(buf[i]);
+    }
+    return 0;
+}

Userland/sh.cpp

@@ -16,10 +16,21 @@ static int runcmd(char* cmd)
 {
     if (cmd[0] == 0)
         return 0;
-    //printf("command: '%s'\n", cmd);
     char buf[128];
     sprintf(buf, "/bin/%s", cmd);
-    int ret = spawn(buf);
+
+    const char* argv[32];
+    size_t argi = 1;
+    argv[0] = &buf[0];
+    size_t buflen = strlen(buf);
+    for (size_t i = 0; i < buflen; ++i) {
+        if (buf[i] == ' ') {
+            buf[i] = '\0';
+            argv[argi++] = &buf[i + 1];
+        }
+    }
+    argv[argi + 1] = nullptr;
+    int ret = spawn(argv[0], argv);
     if (ret == -1) {
         printf("spawn failed: %s (%s)\n", cmd, strerror(errno));
         return 1;