From 6ff749e62652103b3ab84ef145691602ed6e0fea Mon Sep 17 00:00:00 2001
From: Laurent Bercot <ska-skaware@skarnet.org>
Date: Thu, 11 Feb 2021 17:01:39 +0000
Subject:  Add helpful error messages on loopwhilex { block } (and ifte too)

---
 src/execline/ifte.c       | 8 +++++++-
 src/execline/loopwhilex.c | 9 ++++++++-
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/src/execline/ifte.c b/src/execline/ifte.c
index d263a4a..1412bf0 100644
--- a/src/execline/ifte.c
+++ b/src/execline/ifte.c
@@ -1,5 +1,6 @@
 /* ISC license. */
 
+#include <errno.h>
 #include <sys/wait.h>
 
 #include <skalibs/sgetopt.h>
@@ -41,7 +42,12 @@ int main (int argc, char const **argv, char const *const *envp)
   if (argc1 + argc2 + 2 >= argc) strerr_dief1x(100, "empty command-if") ;
 
   pid = el_spawn0(argv[argc1 + argc2 + 2], argv + argc1 + argc2 + 2, envp) ;
-  if (!pid) strerr_diefu2sys(111, "spawn ", argv[argc1 + argc2 + 2]) ;
+  if (!pid)
+  {
+    if (errno == ENOENT && argv[argc1 + argc2 + 2][0] == ' ')
+      strerr_diefu3x(111, "spawn ", argv[argc1 + argc2 + 2], ": name begins with a space, are you trying to spawn a block as your command-if?") ;
+    else strerr_diefu2sys(111, "spawn ", argv[argc1 + argc2 + 2]) ;
+  }
   if (wait_pid(pid, &wstat) == -1)
     strerr_diefu2sys(111, "wait for ", argv[argc1 + argc2 + 2]) ;
   if (!flagnormalcrash && WIFSIGNALED(wstat))
diff --git a/src/execline/loopwhilex.c b/src/execline/loopwhilex.c
index 93a71e0..5add5e5 100644
--- a/src/execline/loopwhilex.c
+++ b/src/execline/loopwhilex.c
@@ -1,5 +1,7 @@
 /* ISC license. */
 
+#include <errno.h>
+
 #include <skalibs/sgetopt.h>
 #include <skalibs/strerr2.h>
 #include <skalibs/types.h>
@@ -58,7 +60,12 @@ int main (int argc, char const *const *argv, char const *const *envp)
   while (cont)
   {
     pid_t pid = el_spawn0(argv[0], argv, envp) ;
-    if (!pid) strerr_diefu2sys(111, "spawn ", argv[0]) ;
+    if (!pid)
+    {
+      if (errno == ENOENT && argv[0][0] == ' ')
+        strerr_diefu3x(111, "spawn ", argv[0], ": name begins with a space, are you trying to spawn a block as your loop body?") ;
+      else strerr_diefu2sys(111, "spawn ", argv[0]) ;
+    }
     if (wait_pid(pid, &wstat) < 0) strerr_diefu1sys(111, "wait_pid") ;
     cont = not != isok(okcodes, nbc, wait_estatus(wstat)) ;
   }
-- 
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