Merge branch 'cow' into net

Conflicts:
	.gitignore
	Makefile
	conf/lab.mk
	kernel/defs.h
	kernel/syscall.c
	kernel/vm.c
	user/pingpong.c
	user/user.h
	user/usys.pl

1 files changed, 60 insertions, 0 deletions

diff --git a/user/xargs.c b/user/xargs.c
new file mode 100644
index 0000000..b5b9bee
--- /dev/null
+++ b/user/xargs.c
@@ -0,0 +1,60 @@
+#include "kernel/types.h"
+
+#include "kernel/param.h"
+#include "kernel/stat.h"
+#include "user/user.h"
+
+#define is_blank(chr) (chr == ' ' || chr == '\t')
+
+int
+main(int argc, char* argv[])
+{
+  char buf[2048], ch;
+  char* p = buf;
+  char* v[MAXARG];
+  int c;
+  int blanks = 0;
+  int offset = 0;
+
+  if (argc <= 1) {
+    fprintf(2, "usage: xargs <command> [argv...]\n");
+    exit(1);
+  }
+
+  for (c = 1; c < argc; c++) {
+    v[c - 1] = argv[c];
+  }
+  --c;
+
+  while (read(0, &ch, 1) > 0) {
+    if (is_blank(ch)) {
+      blanks++;
+      continue;
+    }
+
+    if (blanks) {
+      buf[offset++] = 0;
+
+      v[c++] = p;
+      p = buf + offset;
+
+      blanks = 0;
+    }
+
+    if (ch != '\n') {
+      buf[offset++] = ch;
+    } else {
+      v[c++] = p;
+      p = buf + offset;
+
+      if (!fork()) {
+        exit(exec(v[0], v));
+      }
+      wait(0);
+
+      c = argc - 1;
+    }
+  }
+
+  exit(0);
+}