to_erl: Include strerror(errno) in error messages

to_erl likes to print the message "No running Erlang on pipe ...",
no matter what the problem actually was. The wording might make
you forget that you just need to run to_erl as another user,
for example.

With this change, to_erl will print the system error message
in addition to its own.

Example output:

No running Erlang on pipe pipes/erlang.pipe.5: Permission denied
(wrong user, wrong permissions, etc)

No running Erlang on pipe pipes/erlang.pipe.5: No such device or address
(this actually means "no running Erlang")

No running Erlang on pipe pipes/erlang.pipe: No such file or directory
(not only is there no running Erlang, there are also no pipes at all)

1 files changed, 3 insertions, 3 deletions

diff --git a/erts/etc/unix/to_erl.c b/erts/etc/unix/to_erl.c
index 588d127445..886b301997 100644
--- a/erts/etc/unix/to_erl.c
+++ b/erts/etc/unix/to_erl.c
@@ -164,7 +164,7 @@ int main(int argc, char **argv)
 
 	dirp = opendir(pipename);
 	if(!dirp) {
-	    fprintf(stderr, "Can't access pipe directory %s.\n", pipename);
+	    fprintf(stderr, "Can't access pipe directory %s: %s\n", pipename, strerror(errno));
 	    exit(1);
 	}
 
@@ -205,7 +205,7 @@ int main(int argc, char **argv)
 #ifdef DEBUG
 	fprintf(stderr, "Could not open FIFO %s for reading.\n", FIFO1);
 #endif
-	fprintf(stderr, "No running Erlang on pipe %s.\n", pipename);
+	fprintf(stderr, "No running Erlang on pipe %s: %s\n", pipename, strerror(errno));
 	exit(1);
     }
 #ifdef DEBUG
@@ -216,7 +216,7 @@ int main(int argc, char **argv)
 #ifdef DEBUG
 	fprintf(stderr, "Could not open FIFO %s for writing.\n", FIFO2);
 #endif
-	fprintf(stderr, "No running Erlang on pipe %s.\n", pipename);
+	fprintf(stderr, "No running Erlang on pipe %s: %s\n", pipename, strerror(errno));
 	close(rfd);
 	exit(1);
     }