Bug fix:

-j 1 ran 2 jobs. Should of course only run 1 job

parallel

@@ -6,7 +6,7 @@ parallel - build and execute command lines from standard input in parallel
 
 =head1 SYNOPSIS
 
-B<parallel> [-0cfgqsuvx] [-j num] [command [arguments]] < list_of_arguments
+B<parallel> [-0cfgqsuvxX] [-j num] [command [arguments]] < list_of_arguments
 
 =head1 DESCRIPTION
 
@@ -176,6 +176,7 @@ is a better solution:
   find . -name '*.jpg' | parallel -j +0 convert -geometry 120 {} {}_thumb.jpg
   find . -name '*_thumb.jpg' | ren 's:/([^/]+)_thumb.jpg$:/thumb_$1:'
 
+
 =head1 EXAMPLE 4: Substitution and redirection
 
 This will compare all files in the dir to the file foo and save the
@@ -200,6 +201,29 @@ To put the output in a file called <name>.dir:
 
 B<ls | parallel '(echo -n {}" "; ls {}|wc -l) >>B< {}.dir'>
 
+
+=head1 EXAMPLE 6: Context replace
+
+To remove the files I<pict1000.jpg> .. I<pict9999.jpg> you could do:
+
+B<seq 1000 9999 | parallel rm pict{}.jpg>
+
+You could also do:
+
+B<seq 1000 9999 | perl -pe 's/(.*)/pict$1.jpg/' | parallel -x rm>
+
+The first will run B<rm> 8999 times, while the last will only run
+B<rm> as many times needed to keep the command line length short
+enough.
+
+You could also run:
+
+B<seq 1000 9999 | parallel -X rm pict{}.jpg>
+
+This will also only run B<rm> as many times needed to keep the command
+line length short enough.
+
+
 =head1 QUOTING
 
 For more advanced use quoting may be an issue. The following will
@@ -531,7 +555,9 @@ sub compute_number_of_processes {
     # Number of processes wanted and limited by system ressources
     my $opt_j = shift;
     my $wanted_processes = user_requested_processes($opt_j);
+    debug("Wanted procs: $wanted_processes\n");
     my $system_limit = processes_available_by_system_limit($wanted_processes);
+    debug("Limited to procs: $system_limit\n");
     return $system_limit;
 }
 
@@ -594,21 +620,21 @@ sub processes_available_by_system_limit {
 	    $system_limit = int ($system_limit * 0.9)+1;
 	    $spawning_too_slow = 1;
 	}
-    } while($system_limit <= $wanted_processes 
+    } while($system_limit < $wanted_processes 
 	    and defined $next_command_line
 	    and $more_filehandles
 	    and not $max_system_proc_reached
 	    and not $spawning_too_slow);
-    if($system_limit <= $wanted_processes and not $more_filehandles) {
+    if($system_limit < $wanted_processes and not $more_filehandles) {
 	print STDERR ("Warning: Only enough filehandles to run ",
 		      $system_limit, " jobs in parallel. ",
 		      "Raising ulimit -n may help\n");
     }
-    if($system_limit <= $wanted_processes and $max_system_proc_reached) {
+    if($system_limit < $wanted_processes and $max_system_proc_reached) {
 	print STDERR ("Warning: Only enough available processes to run ",
 		      $system_limit, " jobs in parallel.\n");
     }
-    if($system_limit <= $wanted_processes and $spawning_too_slow) {
+    if($system_limit < $wanted_processes and $spawning_too_slow) {
 	print STDERR ("Warning: Starting 10 extra processes takes > 1 sec.\n",
 		      "Limiting to ", $system_limit, " jobs in parallel.\n");
     }
@@ -894,7 +920,7 @@ sub die_usage {
 
 sub usage {
     print "Usage:\n";
-    print "parallel [-0cfgqsuvx] [command [arguments]] < list_of_arguments\n";
+    print "parallel [-0cfgqsuvxX] [-j num] [command [arguments]] < list_of_arguments\n";
 }
 
 #

parallel.1

@@ -124,7 +124,7 @@
 .\" ========================================================================
 .\"
 .IX Title "PARALLEL 1"
-.TH PARALLEL 1 "2009-03-16" "perl v5.10.0" "User Contributed Perl Documentation"
+.TH PARALLEL 1 "2009-04-04" "perl v5.10.0" "User Contributed Perl Documentation"
 .\" For nroff, turn off justification.  Always turn off hyphenation; it makes
 .\" way too many mistakes in technical documents.
 .if n .ad l
@@ -133,7 +133,7 @@
 parallel \- build and execute command lines from standard input in parallel
 .SH "SYNOPSIS"
 .IX Header "SYNOPSIS"
-\&\fBparallel\fR [\-0cfgqsuvx] [\-j num] [command [arguments]] < list_of_arguments
+\&\fBparallel\fR [\-0cfgqsuvxX] [\-j num] [command [arguments]] < list_of_arguments
 .SH "DESCRIPTION"
 .IX Header "DESCRIPTION"
 For each line of input \fBparallel\fR will execute \fBcommand\fR with the
@@ -306,6 +306,26 @@ files in each directory:
 To put the output in a file called <name>.dir:
 .PP
 \&\fBls | parallel '(echo \-n {}\*(L" \*(R"; ls {}|wc \-l) \fR>\fB {}.dir'\fR
+.SH "EXAMPLE 6: Context replace"
+.IX Header "EXAMPLE 6: Context replace"
+To remove the files \fIpict1000.jpg\fR .. \fIpict9999.jpg\fR you could do:
+.PP
+\&\fBseq 1000 9999 | parallel rm pict{}.jpg\fR
+.PP
+You could also do:
+.PP
+\&\fBseq 1000 9999 | perl \-pe 's/(.*)/pict$1.jpg/' | parallel \-x rm\fR
+.PP
+The first will run \fBrm\fR 8999 times, while the last will only run
+\&\fBrm\fR as many times needed to keep the command line length short
+enough.
+.PP
+You could also run:
+.PP
+\&\fBseq 1000 9999 | parallel \-X rm pict{}.jpg\fR
+.PP
+This will also only run \fBrm\fR as many times needed to keep the command
+line length short enough.
 .SH "QUOTING"
 .IX Header "QUOTING"
 For more advanced use quoting may be an issue. The following will