Diagnose missing argument in :w, :a and :!.

1 files changed, 8 insertions, 2 deletions

diff --git a/pw.c b/pw.c
index cb1c4cd..fdd5846 100644
--- a/pw.c
+++ b/pw.c
@@ -250,7 +250,10 @@ static void execute(char *cmd)
 
   switch (cmd[1]) {
   case 'w': case 'a':
-    {
+    if (arg[0] == 0) {
+      sprintf(cmd, "file name required!");
+      break;
+    } else {
       FILE *f = fopen(arg, cmd[1] == 'w' ? "w" : "a");
       int ok = 1;
 
@@ -272,7 +275,10 @@ static void execute(char *cmd)
     }
     break;
   case '!':
-    {
+    if (arg[0] == 0) {
+      sprintf(cmd, "command required!");
+      break;
+    } else {
       FILE *p = popen(arg, "w");
       int ok = 1;