parallel: added $PARALLEL_SSH.

src/parallel

@@ -5387,6 +5387,8 @@ sub sshcommand_of_sshlogin {
     #   login@host
     my $self = shift;
     my ($sshcmd, $serverlogin);
+    # If $SSH is unset, use 'ssh'
+    $ENV{'PARALLEL_SSH'} ||= "ssh";
     if($self->{'string'} =~ /(.+) (\S+)$/) {
         # Own ssh command
         $sshcmd = $1; $serverlogin = $2;
@@ -5395,7 +5397,7 @@ sub sshcommand_of_sshlogin {
         if($opt::controlmaster) {
             # Use control_path to make ssh faster
             my $control_path = $self->control_path_dir()."/ssh-%r@%h:%p";
-            $sshcmd = "ssh -S ".$control_path;
+            $sshcmd = $ENV{'PARALLEL_SSH'}." -S ".$control_path;
             $serverlogin = $self->{'string'};
             if(not $self->{'control_path'}{$control_path}++) {
                 # Master is not running for this control_path
@@ -5407,18 +5409,24 @@ sub sshcommand_of_sshlogin {
 		    $SIG{'TERM'} = undef;
                     # Ignore the 'foo' being printed
                     open(STDOUT,">","/dev/null");
-                    # OpenSSH_3.6.1p2 gives 'tcgetattr: Invalid argument' with -tt
+                    # With -tt OpenSSH_3.6.1p2 gives:
-                    # STDERR >/dev/null to ignore "process_mux_new_session: tcgetattr: Invalid argument"
+		    # 'tcgetattr: Invalid argument'
+                    # STDERR >/dev/null to ignore
+		    # "process_mux_new_session: tcgetattr: Invalid argument"
                     open(STDERR,">","/dev/null");
                     open(STDIN,"<","/dev/null");
-                    # Run a sleep that outputs data, so it will discover if the ssh connection closes.
+                    # Run a sleep that outputs data, so it will discover
-                    my $sleep = ::shell_quote_scalar('$|=1;while(1){sleep 1;print "foo\n"}');
+		    # if the ssh connection closes.
-                    my @master = ("ssh", "-tt", "-MTS", $control_path, $serverlogin, "perl", "-e", $sleep);
+                    my $sleep = ::shell_quote_scalar
+			('$|=1;while(1){sleep 1;print "foo\n"}');
+                    my @master = ($ENV{'PARALLEL_SSH'}, "-tt", "-MTS",
+				  $control_path, $serverlogin, "perl", "-e",
+				  $sleep);
                     exec(@master);
                 }
             }
         } else {
-            $sshcmd = "ssh"; $serverlogin = $self->{'string'};
+            $sshcmd = $ENV{'PARALLEL_SSH'}; $serverlogin = $self->{'string'};
         }
     }
     $self->{'sshcommand'} = $sshcmd;

src/parallel.pod

@@ -697,9 +697,9 @@ See also: B<--line-buffer> B<--ungroup>
 Print a summary of the options to GNU B<parallel> and exit.
 
 
-=item B<--halt-on-error> I<val>
+=item B<--halt-on-error> I<val> (alpha testing)
 
-=item B<--halt> I<val>
+=item B<--halt> I<val> (alpha testing)
 
 When should GNU B<parallel> terminate? In some situations it makes no
 sense to run all jobs. GNU B<parallel> should simply give up as soon
@@ -1665,7 +1665,7 @@ Does not run the command but quotes it. Useful for making quoted
 composed commands for GNU B<parallel>.
 
 
-=item B<--shuf> (beta testing)
+=item B<--shuf> (alpha testing)
 
 Shuffle jobs. When having multiple input sources it is hard to
 randomize jobs. --shuf will generate all jobs, and shuffle them before
@@ -3439,6 +3439,13 @@ $SHELL. If undefined use:
 =back
 
 
+=item $PARALLEL_SSH (alpha testing)
+
+GNU B<parallel> defaults to using B<ssh> for remote access. This can
+be overridden with $PARALLEL_SSH. It can also be set on a per server
+basis (see B<--sshlogin>).
+
+
 =item $PARALLEL_SEQ
 
 $PARALLEL_SEQ will be set to the sequence number of the job

testsuite/tests-to-run/parallel-local-ssh1.sh

@@ -61,6 +61,11 @@ echo '### bug #40001: --joblog and --nonall seem not to work together:'
 echo '### bug #40132: FreeBSD: --workdir . gives warning if . == $HOME'
   cd && parallel --workdir . -S lo pwd ::: ""
 
+echo '### use function as $PARALLEL_SSH'
+  foossh() { echo "FOOSSH" >&2; ssh "$@"; }; 
+  export -f foossh; 
+  PARALLEL_SSH=foossh parallel -S 1/lo echo ::: 'Run through FOOSSH?'
+
 echo '### test filename :'
   echo content-of-: > :; 
   echo : | parallel -j1 --trc {}.{.} -S parallel@lo '(echo remote-{}.{.};cat {}) > {}.{.}'; 

testsuite/wanted-results/parallel-local-ssh1

@@ -84,6 +84,11 @@ echo '### bug #40132: FreeBSD: --workdir . gives warning if . == $HOME'
 ### bug #40132: FreeBSD: --workdir . gives warning if . == $HOME
   cd && parallel --workdir . -S lo pwd ::: ""
 /home/tange
+echo '### use function as $PARALLEL_SSH'
+### use function as $PARALLEL_SSH
+  foossh() { echo "FOOSSH" >&2; ssh "$@"; };   export -f foossh;   PARALLEL_SSH=foossh parallel -S 1/lo echo ::: 'Run through FOOSSH?'
+Run through FOOSSH?
+FOOSSH
 echo '### test filename :'
 ### test filename :
   echo content-of-: > :;   echo : | parallel -j1 --trc {}.{.} -S parallel@lo '(echo remote-{}.{.};cat {}) > {}.{.}';   cat :.:; rm : :.: