ITNW 2310 - PERL
Allan Kochis,Adjunct Professor - CIT

Functions aka subroutines

  1. Named and default arguments
    PerlOutput 
    #!/usr/bin/perl
#
#
#  Named and default parameters
#
sub area {
    %args=@_;
    my($length,$width,$area);
    $length=$args{"length"} ? $args{"length"} : 20;
    $width=$args{"width"} ? $args{"width"} : 20;
    print "_" x 20 ."\n";
    print "Length = ".$length."\n";
    print "Width  = ".$width."\n";
    print "Area   = ".$length*$width."\n";
    print "_" x 20 ."\n";
}

area();
area("length",30);
area(width=>50);
area(lenght=>100,width=>34);
area("width",56,"length",67);




    ____________________
Length = 20
Width  = 20
Area   = 400
____________________
____________________
Length = 30
Width  = 20
Area   = 600
____________________
____________________
Length = 20
Width  = 50
Area   = 1000
____________________
____________________
Length = 20
Width  = 34
Area   = 680
____________________
____________________
Length = 67
Width  = 56
Area   = 3752
____________________

  2. Multiple Requires
    PerlOutput 
    #!/usr/bin/perl -w

require 'sub7a.pl';
require 'sub7b.pl';

print "------------------------------\n";
print ` cat sub7a.pl`;
print "------------------------------\n";
print `cat sub7b.pl`;
print "------------------------------\n";

$var=7;

print addtwo($var)."\n";

print addthree($var)."\n";


    ------------------------------
#!/usr/bin/perl -w
require "sub7b.pl";

sub addtwo {
  my $var=$_[0];
  $var+=2;
  return $var;
}

#
# always include this
#
1;
------------------------------
#!/usr/bin/perl -w


sub addthree {
 my $var=$_[0];
  $var+=3;
  return $var;
}
#
# always include this
#
1;
------------------------------
9
10

  3. Lexical Collisions
    PerlOutput 
    #!/usr/bin/perl -w

require 'sub8.pl';

print "------------------------------\n";
print ` cat sub8.pl`;
print "------------------------------\n";

$var=7;

print addtwo($var)."\n";

print addthree($var)."\n";


    ------------------------------
#!/usr/bin/perl -w

sub addtwo {
  $var=$_[0];
  $var+=2;
  return $var;
}

sub addthree {
  $var=$_[0];
  $var+=3;
  return $var;
}
#
# always include this
#
1;
------------------------------
9
12

  4. Packages
    PerlOutput 
    #!/usr/bin/perl -w

require 'sub9.pl';

sub addtwo {
   my $var=$_[0];
   $var--;
}
print "------------------------------\n";
print ` cat sub9.pl`;
print "------------------------------\n";

$var=7;

print perly::addtwo($var)."\n";

print perly::addthree($var)."\n";
 
print addtwo($var)."\n";


    ------------------------------
#!/usr/bin/perl -w
package perly;
sub addtwo {
  $var=$_[0];
  $var+=2;
  return $var;
}

sub addthree {
  $var=$_[0];
  $var+=3;
  return $var;
}
#
# always include this
#
1;
------------------------------
9
10
7

  5. System Functions
    PerlOutput 
    #!/usr/bin/perl -w
#
#
#  Read /etc/passwd
#
setpwent; # start lookup

while(@pw=getpwent) {
#
#  returns ($name,$passwd,$uid,$gid,$quota,$comment,$gcos,$dir,$shell)
#
    print $pw[6]."\t".$pw[0]."\n" if ($pw[6]);
}

endpwent;


    root    root
bin     bin
daemon  daemon
adm     adm
lp      lp
sync    sync
shutdown        shutdown
halt    halt
mail    mail
news    news
uucp    uucp
operator        operator
games   games
gopher  gopher
FTP User        ftp
Nobody  nobody
virtual console memory owner    vcsa
NSCD Daemon     nscd
Privilege-separated SSH sshd
Portmapper RPC user     rpc
RPC Service User        rpcuser
Anonymous NFS User      nfsnobody
Apache  apache
X Font Server   xfs
Named   named
desktop desktop
Allan Kochis    kochis
Jeremy Stockman,,512-682-7631,512-291-0114      ps3167901
Tommy Heaney,ITNW 2310,T&TH 705,512-635-3942    ps3167904
Montgomery Conner,,,(512) 659-9367      ps3167907
Aaron Rivas     ps3167908
Arturo F. Dominguez     ps3167911
Charles Egner,null,null,512-589-5927    ps3167913
Andrew McDonald,5126448494,5126448494   ps3167916


    PerlOutput 
    #!/usr/bin/perl
#
#
#  Read /etc/group
#
setgrent; # start lookup
$governor=0;
while(($name,$pw,$gid,$members)=getgrent) {
    print $name."\n";
    last if ($governor++ > 10);
}

endgrent;


    root
bin
daemon
sys
adm
tty
disk
lp
mem
kmem
wheel
mail

    PerlOutput 
    #!/usr/bin/perl
#
#
#  login
#
$whoami=getlogin;

print $whoami."\n";



    kochis


    PerlOutput 
    #!/usr/bin/perl
#
#
#  timing
#
sub timer {
    print "-" x 20 ."\n";
    ($user,$system,$cuser,$csystem)=times;
    print $user."\n";
    print $system."\n";
    print "-" x 20 ."\n";
}

&timer;
for($outer=0;$outer

    

    --------------------
0
0
--------------------
--------------------
27.93
127.67
--------------------

  6. Function names
    PerlOutput 
    #!/usr/bin/perl
#
#
#  Where am I?
#
# ($package,$filename,$line,$subr,$has_args,$wantarray)
#
sub f1 {
   $a=(caller(0))[3];
   print "I am in function ".$a."\n";
}
sub f2 {
   $a=(caller(0))[3];
   print "I am in function ".$a."\n";
}
sub f3 {
   $a=(caller(0))[3];
   print "I am in function ".$a."\n";
}
sub f4 {
   $a=(caller(0))[3];
   print "I am in function ".$a."\n";
}
sub f5 {
   $a=(caller(0))[3];
   print "I am in function ".$a."\n";
}
f1();
f3();
f5();
f4();
f2();


    I am in function main::f1
I am in function main::f3
I am in function main::f5
I am in function main::f4
I am in function main::f2
© Allan Kochis Last revision 10/6/2005