1 : #!/usr/local/bin/perl
2 :
3 : open (WOUT, "w|");
4 : $time = <WOUT>;
5 : $time =~ s/^ *//;
6 : $time =~ s/ .*//;
7 : ; # skip headings line
8 : @users = ;
9 : close (WOUT);
10: foreach $user (@users) {
11:   $user =~ s/ .*//;
12: }
13: print ("Current time: $time");
14: print ("Users logged on:\n");
15: $prevuser = "";
16: foreach $user (sort @users) {
17:   if ($user ne $prevuser) {
18:     print ("\t$user");
19:     $prevuser = $user;
20:   }
21: }

Current time: 4:25pm
Users logged on:
  dave
  kilroy
  root
  zarquon

4:25pm  up 1 day,  6:37,  6 users,  load average: 0.79, 0.36, 0.28
User     tty       login@  idle   JCPU   PCPU what
dave     ttyp0     2:26pm           27      3 w
kilroy   ttyp1     9:01am  2:27   1:04     11 -csh
kilroy   ttyp2     9:02am    43   1:46     27 rn
root     ttyp3     4:22pm     2               -csh
zarquon  ttyp4     1:26pm     4     43     16 cc myprog.c
kilroy   ttyp5     9:03am         2:14     48 /usr/games/hack

1: #!/usr/local/bin/perl
2:
3: open (STDOUT, ">file1") || die ("open STDOUT failed");
4: open (STDERR, ">&STDOUT") || die ("open STDERR failed");
5: print STDOUT ("line 1\n");
6: print STDERR ("line 2\n");
7: close (STDOUT);
8: close (STDERR);

1 : #!/usr/local/bin/perl
2 :
3 : open (STDOUT, ">file1") || die ("open STDOUT failed");
4 : open (STDERR, ">&STDOUT") || die ("open STDERR failed");
5 : $| = 1;
6 : select (STDERR);
7 : $| = 1;
8 : print STDOUT ("line 1\n");
9 : print STDERR ("line 2\n");
10: close (STDOUT);
11: close (STDERR);

1: #!/usr/local/bin/perl
2:
3: while ($line = <>) {
4:   print ($line);
5:   if (eof) {
6:     print ("-- end of current file --\n");
7:   }
8: }

$ program file1 file2
This is a line from the first file.
Here is the last line of the first file.
-- end of current file --
This is a line from the second and last file.
Here is the last line of the last file.
-- end of current file --
$

1: #!/usr/local/bin/perl
2:
3: while ($line = <>) {
4:   print ($line);
5:   if (eof()) {
6:     print ("-- end of output --\n");
7:   }
8: }

$ program file1 file2
This is a line from the first file.
Here is the last line of the first file.
This is a line from the second and last file.
Here is the last line of the last file.
-- end of output --$

1: #!/usr/local/bin/perl
2:
3: &open_file("INFILE", "", "file1");
4: &open_file("OUTFILE", ">", "file2");
5: while ($line = &read_from_file("INFILE")) {
6:   &print_to_file("OUTFILE", $line);
7: }
8:
9: sub open_file {
10:   local ($filevar, $filemode, $filename) = @_;
11:
12:   open ($filevar, $filemode . $filename) ||
13:     die ("Can't open $filename");
14: }
15: sub read_from_file {
16:   local ($filevar) = @_;
17:
18:   <$filevar>;
19: }
20: sub print_to_file {
21:   local ($filevar, $line) = @_;
22:
23:   print $filevar ($line);
24: }