Executing bash script, read its output and create html with Perl - perl

Question

I have a bash script which produces different integer values. When I run that script, the output looks like this:
12
34
34
67
6
This script runs on a Solaris server. In order to provide other users in the network with these values, I decided to write a Perl script which can:
run the bash file
read its output
build a tiny html page with a table in which the bash values are stored
Thats a hard job for me because I have almost no experience with Perl. I know I can use system to execute unix commands (and bash files) but I cannot get the output. I also heared about qx which sounds very useful for my case.
But I must admit I have no clue how do start... Could you give me a few hints how to solve that?

Answer 1

With a question like this it's a little hard to know where to begin.
The qx to which you are referring is a feature of Perl. The "q*" or "Quote and Quote-like Operators" are documented in the Perl "operators" man page (normally you'd use man perlop to read that on systems with a conventional installation of Perl).
Specifically qx is the "quoted-execution of a command" ... which is essentially an alternative form of the ` (back tick or "command substitution") operator in Perl.
In other words if you execute a command like:
perl -e '$foo = qx{ls}; print "\n###\n$foo\n###\n";'
... on a system with Perl installed then it should run Perl, which should evaluate (-e) the expression you've provided (quoted). In other words we're writing a small program right on the command line. This program starts by creating a variable whose contents will be a "scalar" (which is Perl terminology for a string or number). We're assigning (the =, or assignment, operator) the output which is captured by executing the ls command back to this variable ($foo). After that we're printing the contents of our variable (whatever the ls command would have printed) with ### lines preceding and following those contents..
A quirk of Perl's qx operator (and the various other q* operators) is that it allows you to delimit the command with just about any characters you like. For example perl -e '$bar = qx/pwd/;' would capture the output of the pwd command. When you use any of the characters that are normally used as delimiters around text parentheses, braces, brackets, etc) then the qx command will look for the appropriate matching delimiter. If you use any other punctuation (or non-alpha-numeric character?) then that same character will be the terminating delimiter as well. This later behavior is similar to, and was inspired by, a feature in "substitution" command from the old sed utility and ed line editors; while the matching of parentheses, braces, etc. are a Perl novelty.
So that's the basics of how to capture your shell script's output. To print the numbers in an HTML table you'd have to split the captured output into separate lines (saving them into a list or array) then print your HTML prologue (the <table> and <th> (header) tags, and so on) ... them loop over a series of <tr> rows, interpolating your numbers into <td>> (table data) containers) and then finally print your HTML epilogue (with the closing tags).
For that you'll want to read up on the Perl print function and about "interpolation" in Perl. That's a fairly complex topic.
This is all extremely crude and there are tools around which allow you to approach the generation of HTML at a much higher level. It's also rather dubious that you want to wrap the execution of your shell script in a Perl script since it seems likely that you could modify the shell script to directly output HTML (perhaps as an option controlled by a command line switch or environment variable) or that you could re-write the shell script in Perl. This could potentially eliminate the extra work of parsing the output (splitting it into lines and separating the values out of those lines into an array because you can capture the data directly into the array (or possibly print out your HTML rows) directly as you are generating them (however your existing shell script is doing that).

Answer 2

To capture the output of your bash file, you can use the backtick operator:
use strict;
my $e = `ls`;
print $e;

Answer 3

Many, many thanks to you! With your great help. I was able to build a perl script which does a big part of the job.
This is what I have created so far:
#!/usr/bin/perl -w
use strict;
use CGI qw(:standard);
#some variables
my $message = "please wait, loading data...\n";
#First build the web page
print header;
print start_html('Hello World');
print "<H1>we need love, peace and harmony</H1>\n";
print "<p>$message</p>\n";
#Establish a pipeline between the bash and my script.
my $bash_command = '/love/peace/harmony/./lovepeace.bash';
open(my $pipe, '-|', $bash_command) or die $!;
while (my $line = <$pipe>){
# Do something with each line.
print "<p>$line</p>\n";
}
#job done, now refresh page?
print end_html;
When I call that .pl script in my browser, everything works nice :-) But a few questions are still on my mind:
When I call this website, it is busy loading the values from the pipe. Since there are about 10 Values its rather
quick (2-4 seconds) But if I have 100+ Values the user has to wait a while. Since I cannot have a progress bar, I
should give an information to the user. Like:
"Loading data, please wait..."
And when the job is done, this message should say: "Job done" or something similar.
But how do I realize if the process is finnished?
can I reload the page if the job is done ?
Is there any chance of using my own stylesheet wihtin this perl-CGI
Regards,
JJ

Answer 4

Why only perl:
you can use awk for that in side your shell script itself.
I have done this earlier.
if you have the out put values in a variable then use the below method:
echo $SUBSCRIBERS|awk 'BEGIN {
print "<?xml version=\"1.0\" encoding=\"UTF-8\"?><GenTransactionHandler xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\"><EntityToPublish>\n<Entitytype=\"C\" typeDesc=\"Subscriber level\"><TargetApplCode>UHUNLD</TargetApplCode><TrxName>GET_SUBSCR_DATA</TrxName>"
}
{for(i=1;i<NF+1;i++) printf("<value>%d</value>\n",$i)}
END{
print "</Entity>\n</EntityToPublish></GenTransactionHandler>"}' >XML_SUB_NUM`date +%Y%m%d%H%M%S`.xml
in $SUBSCRIBERS the values should eb tab separated.