bug #35069: --pipe without command should give reasonable error message.

src/parallel

@@ -131,7 +131,6 @@ for my $sshlogin (values %Global::host) {
     $sshlogin->max_jobs_running();
 }
 
-
 init_run_jobs();
 my $sem;
 if($Global::semaphore) {
@@ -4221,18 +4220,26 @@ sub get {
 	    );
 	$cmd_line->populate();
 	::debug("cmd_line->number_of_args ".$cmd_line->number_of_args()."\n");
-	if(not $::opt_pipe and $cmd_line->number_of_args() == 0) {
+	if($::opt_pipe) {
+	    if($cmd_line->replaced() eq "") {
+		# Empty command - pipe requires a command
+		print STDERR "$Global::progname: --pipe must have a ".
+		    "command to pipe into (e.g. 'cat')\n";
+		::wait_and_exit(255);
+	    }
+	} else {
+	    if($cmd_line->number_of_args() == 0) {
 		# We did not get more args - maybe at EOF string?
 		return undef;
 	    } elsif($cmd_line->replaced() eq "") {
 		# Empty command - get the next instead
 		return $self->get();
-	} else {
+	    }
+	}
 	$self->set_seq($self->seq()+1);
 	return $cmd_line;
     }
 }
-}
 
 sub unget {
     my $self = shift;

testsuite/tests-to-run/test30.sh

@@ -19,4 +19,7 @@ seq 2 | stdout parallel -X --eta echo
 
 echo '### --timeout on remote machines'
 parallel -j0 --timeout 3 --onall -S .. 'sleep {}; echo {}' ::: 1 6 7 ; echo $?
+
+echo '### --pipe without command'
+seq -w 10 | stdout parallel --pipe
 EOF

testsuite/wanted-results/test30

@@ -22,3 +22,5 @@ Computers / CPU cores / Max jobs to run
 1
 1
 2
+### --pipe without command
+parallel: --pipe must have a command to pipe into (e.g. 'cat')

testsuite/wanted-results/test33

@@ -12,6 +12,7 @@ cat ... | parallel --pipe [options] [command [arguments]]
 {3} {3.} {3/} {3/.}  Positional replacement strings
 
 -S sshlogin    Example: foo@server.example.com
+--slf ..       Use ~/.parallel/sshloginfile as the list of sshlogins
 --trc {}.bar   Shorthand for --transfer --return {}.bar --cleanup
 --onall        Run the given command with argument on all sshlogins
 --nonall       Run the given command with no arguments on all sshlogins