perl examples

Perl Examples

1. Calling System Commands
* Image Processing
* Renaming Files
* File Conversion
* Creating Directories
* Padding & Unpadding Files

2. Scanning the Network
* Finding Free Machines
* Finding Processes
* Finding Files
* Finding Users

3. File Manipulation
* Generating HTML Files
* Generating Xpost Scripts
* Modifying Files
* Convert Raw Data

Remember: In order to be able to run your perl script, it must begin with the line:

#!/usr/local/bin/perl

Furthermore, if you've named the file "myFile", then to make the file executable, you need to type in a unix window:

chmod 755 myFile

Image Processing

#!/usr/local/bin/perl
#
# composite series of images over a background image
#

if ($#ARGV != 4) {
print "usage: compem bg.rgb inbase outbase startNum stopNum\n";
exit;
}

$bg = $ARGV[0];
$inbase = $ARGV[1];
$outbase = $ARGV[2];
$start = $ARGV[3];
$stop = $ARGV[4];

# for each image
for ($i=$start; $i <= $stop; $i++) {

# pad numbers
$num = $i;
if($i<10) { $num = "00$i"; }
elsif($i<100) { $num = "0$i"; }

# call unix command "over"
$cmd = "over $bg $inbase.$num $outbase.$num 0 0";
print $cmd."\n";
if(system($cmd)) { print "over failed\n"; }
}


Renaming Files

#!/usr/local/bin/perl
#
# rename series of frames
#
if ($#ARGV != 3) {
print "usage: rename old new start stop\n";
exit;
}

$old = $ARGV[0];
$new = $ARGV[1];
$start = $ARGV[2];
$stop = $ARGV[3];

for ($i=$start; $i <= $stop; $i++) {

$num = $i;
if($i<10) { $num = "00$i"; }
elsif($i<100) { $num = "0$i"; }

$cmd = "mv $old.$num $new.$num";
print $cmd."\n";
if(system($cmd)) { print "rename failed\n"; }
}


File Conversion

#!/usr/local/bin/perl
#
# convert series of images from one format to another
#
if ($#ARGV != 5) {
print "usage: fconvert intype outtype old new start stop\n";
exit;
}

$intype = $ARGV[0];
$outtype = $ARGV[1];
$old = $ARGV[2];
$new = $ARGV[3];
$start = $ARGV[4];
$stop = $ARGV[5];

for ($i=$start; $i <= $stop; $i++) {

$num = $i;
if($i<10) { $num = "00$i"; }
elsif($i<100) { $num = "0$i"; }

$cmd = "imgcvt -i $intype -o $outtype $old.$num $new.$num";
print $cmd."\n";
if(system($cmd)) { print "imgcvt failed\n"; }
}


Creating Directories

#!/usr/local/bin/perl
#
# create a series of directories
#
if ($#ARGV != 2) {
print "usage: mkdirs base start stop\n";
exit;
}

$base = $ARGV[0];
$start = $ARGV[1];
$stop = $ARGV[2];

for ($i=$start; $i <= $stop; $i++) {

$num = $i;
if($i<10) { $num = "00$i"; }
elsif($i<100) { $num = "0$i"; }

$cmd = "mkdir $base$num";
print $cmd."\n";
if(system($cmd)) { print "mkdir failed\n"; }
}


Padding & Unpadding Files

#!/usr/local/bin/perl
#
# pad file numbers with zeros
#
if ($#ARGV != 2) {
print "usage: pad base start stop\n";
exit;
}

$base = $ARGV[0];
$start = $ARGV[1];
$stop = $ARGV[2];

for ($i=$start; $i <= $stop; $i++) {

$num = $i;
if($i<10) { $num = "00$i"; }
elsif($i<100) { $num = "0$i"; }

$cmd = "mv $base$i $base$num";

# to unpad, use this instead:
# $cmd = "mv $base$num $base$i";

print $cmd."\n";
if(system($cmd)) { print "pad failed\n"; }
}


Finding Free Machines

#!/usr/local/bin/perl
#
# search list of machines for machines with no users logged on
#
$machines = `systems sgi`;
chop($machines);
@sgis = split(/ /, $machines);
@sgis = sort(@sgis);

foreach $machine (@sgis) {

if(!(`rusers $machine`)) {
print "$machine\n";
}
}


Finding Processes

#!/usr/local/bin/perl
#
# search for processes running on machines
#

if ($#ARGV != 0) {
print "usage: findprocess process\n";
exit;
}

$process = $ARGV[0];
$machines = `systems sgi`;
chop($machines);
@sgis = split(/ /,$machines);
@sgis = sort(@sgis);

foreach $machine (@sgis) {

print "Checking $machine...\n";

@lines = `rsh $machine \"ps -ef | grep $process | grep -v findprocess | grep -v grep\"`;

if(@lines) {
foreach $line (@lines) {
$line =~ /^\s*(\w+)\s+(\d+)/;
$user = $1;
$pid = $2;
print "$user on $machine pid: $pid\n";
}
}
}


Finding Files

#!/usr/local/bin/perl
#
# search for a file in all subdirectories
#
if ($#ARGV != 0) {
print "usage: findfile filename\n";
exit;
}

$filename = $ARGV[0];

# look in current directory
$dir = `pwd`;
chop($dir);
&searchDirectory($dir);

sub searchDirectory {
local($dir);
local(@lines);
local($line);
local($file);
local($subdir);

$dir = $_[0];

# check for permission
if(-x $dir) {

# search this directory
@lines = `cd $dir; ls -l | grep $filename`;
foreach $line (@lines) {
$line =~ /\s+(\S+)$/;
$file = $1;
print "Found $file in $dir\n";
}

# search any sub directories
@lines = `cd $dir; ls -l`;
foreach $line (@lines) {
if($line =~ /^d/) {
$line =~ /\s+(\S+)$/;
$subdir = $dir."/".$1;
&searchDirectory($subdir);
}
}
}
}


Finding Users

#!/usr/local/bin/perl
#
# check whether user is logged on
#

if ($#ARGV != 0) {
print "usage: finduser username\n";
exit;
}

$username = $ARGV[0];
$machines = "insanity ".`systems sgi`;
chop($machines);
@machines = split(/ /,$machines);
@machines = sort(@machines);

foreach $machine (@machines) {

if(`rusers $machine | grep $username`) {
print "$username logged on $machine\n";
}
}


Generating HTML Files

#!/usr/local/bin/perl
#
# create n html files linked together in slide show
#

if ($#ARGV != 1) {
print "usage: htmlslides base num\n";
exit;
}

$base = $ARGV[0];
$num = $ARGV[1];

for ($i=1; $i <= $num; $i++) {

open(HTML, ">$base$i.html");

if($i==$num) {
$next = 1;
} else {
$next = $i+1;
}

print HTML "\n\n\n\n\n";
print HTML "\n";
print HTML "\n\n";

close(HTML);
}


Generating Xpost Scripts

#!/usr/local/bin/perl
#
# generate an xpost script to adjust saturation, and run xpost
#
if ($#ARGV != 2) {
print "usage: fixsat infile.tiff outfile.tiff satval\n";
exit;
}

$infile = $ARGV[0];
$outfile = $ARGV[1];
$satval = $ARGV[2];

# open xpost script
open(XPOST, ">__tmp.xp");

# set view to register A
print XPOST "view A\n";

# load original image into reg A
print XPOST "load $infile\n";

# run Kmult to turn down saturation
print XPOST "Kmult $satval $satval $satval 1.0 a b\n";

# set view to register B
print XPOST "view B\n";

# save unsaturated image
print XPOST "save tiff $outfile\n";

# close xpost script
close(XPOST);

# run xpost script
$cmd = "xpost -q -s __tmp.xp";
print $cmd."\n";
system($cmd);

# clean up
$cmd = "/bin/rm -f __tmp.xp";
print $cmd."\n";
system($cmd);


Modifying Text Files

#!/usr/local/bin/perl
#
# change all occurances of a string in a file to another string
#

if ($#ARGV != 3) {
print "usage: chstring oldfile newfile oldstring newstring\n";
exit;
}

$oldfile = $ARGV[0];
$newfile = $ARGV[1];
$old = $ARGV[2];
$new = $ARGV[3];

open(OF, $oldfile);
open(NF, ">$newfile");

# read in each line of the file
while ($line = ) {
$line =~ s/$old/$new/;
print NF $line;
}

close(OF);
close(NF);


Convert Raw Timecode Data to Readable Data

#!/usr/local/bin/perl
#
# Change raw timecode data to different format
#
# timecode data event looks like:
#
# Event: 1
# 00:01:05:23
# 00:01:27:21
# a-2-9
#
# Event: 2
# 00:01:56:13
# 00:02:03:19
# a-3-9
#
# ...and so on...
#
# Want to change it to the form:
#
# a-2-9 = 21.93 seconds = 658 frames
# a-3-9 = 7.20 seconds = 216 frames
#

open(FP,"
$first = 1;
$total = 0;

while($line = ) {

if ($line =~ /^\d\d/ && $first) {
$in = $line;
$first = 0;
} elsif ($line =~ /^\d\d/ && !$first) {
$out = $line;
$first = 1;
} elsif ($line =~ /^\w-/) {
$shot = $line;
chop($shot);

# parse timecodes and
# translate in and out into seconds
$in =~ /(\d\d):(\d\d):(\d\d):(\d\d)/;
$hrs = $1;
$mns = $2;
$scs = $3;
$fms = $4;
$inSecs = $hrs * 3600 + $mns * 60 + $scs + $fms / 30;

$out =~ /(\d\d):(\d\d):(\d\d):(\d\d)/;
$hrs = $1;
$mns = $2;
$scs = $3;
$fms = $4;
$outSecs = $hrs * 3600 + $mns * 60 + $scs + $fms / 30;

# calc duration
$dur = $outSecs - $inSecs;
$total += $dur;

# print line
printf("$shot = %.2f seconds = %d frames\n", $dur, $dur * 30);
}
}

print "total = ".($total / 60)." mins\n";

close FP;