When I run the following script I get errors when I use the list form if the system call. Why is this? 
   system('rm test?.out 2> /dev/null');
   print "   ------\n   test 1\n";
   $rc = system('/usr/bin/ps', '>' , 'test1.out', '&');
   print '   rc=',$rc,"\n";
   print "   test1.out not created\n" unless -e 'test1.out';
   print "   ------\n   test 2\n";
   $rc = system('/usr/bin/ps > test2.out &');
   print '   rc=',$rc,"\n";
   print "   test2.out not created\n" unless -e 'test2.out';
   print "   ------\n   test 3\n";
   $rc = system('/usr/bin/ps', '>' , 'test3.out');
   print '   rc=',$rc,"\n";
   print "   test3.out not created\n" unless -e 'test3.out';

[download]
The output is... 
   ------
   test 1
usage: ps [ -aAdeflcjLPy ] [ -o format ] [ -t termlist ]
        [ -u userlist ] [ -U userlist ] [ -G grouplist ]
        [ -p proclist ] [ -g pgrplist ] [ -s sidlist ]
  'format' is one or more of:
        user ruser group rgroup uid ruid gid rgid pid ppid pgid sid ta
+skid
        pri opri pcpu pmem vsz rss osz nice class time etime stime
        f s c lwp nlwp psr tty addr wchan fname comm args projid proje
+ct
   rc=256
   test1.out not created
   ------
   test 2
   rc=0
   ------
   test 3
usage: ps [ -aAdeflcjLPy ] [ -o format ] [ -t termlist ]
        [ -u userlist ] [ -U userlist ] [ -G grouplist ]
        [ -p proclist ] [ -g pgrplist ] [ -s sidlist ]
  'format' is one or more of:
        user ruser group rgroup uid ruid gid rgid pid ppid pgid sid ta
+skid
        pri opri pcpu pmem vsz rss osz nice class time etime stime
        f s c lwp nlwp psr tty addr wchan fname comm args projid proje
+ct
   rc=256
   test3.out not created

[download]
As you can see only Test 2 is successful. Why is this? Is there a correct way to execute a statement with an ampersand as the last char using the list form if system?

These tests were done on a Sun box using Perl 5.8.

edited: Mon Jul 28 18:28:33 2003 by jeffa - code tags

In reply to Trying to understand the System function by mifflin

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