The Perl Utility

Overview

As mentioned in the previous chapter, the perl utility provided by the iSeries Tools for Developers product is a PASE utility. Qshell provides direct support to run PASE utilities without starting a PASE environment or leaving the Qshell environment.

Perl is a truly popular piece of scripting/programming software (covered by the GNU General Public License) that can be used to do just about anything. Larry Wall originally released perl in 1987 as a Unix system-administration tool. It has now reached version 5.8, and runs on dozens of platforms.

Some of perl's many strengths include the following:

  • Broad standard library and third-party libraries
  • Powerful string-processing operators
  • Automatic memory management
  • An eclectic syntax, which provides perl programmers many ways to accomplish the same task

Many books, tutorials, and Web resources are available for learning perl. Start at the perl home page, www.perl.com, and the Comprehensive Perl Archive Network, www.cpan.org, for downloads of perl distributions and modules to do just about anything you could think of.

Perl has also been ported to iSeries as an ILE application (i.e., outside of PASE), but the PASE application is much newer , and the ILE version appears to be less frequently used. The perl utility shipped with iSeries Tools for Developers is version 5.005_03 for AIX. The current version available on CPAN in the OS/400 section is "5.8.0@18380."


Running Perl

If you examine the series of directories that were added to the PATH variable in Figure 21.3 of the previous chapter, you will see the following statement:

# Add the PASE binary locations to the path
export PATH="$PATH:/QIBM/ProdData/DeveloperTools/pase/bin"

This statement sets the path to enable access to Tools for Developers PASE utilities, including perl, in a Qshell resource file. After you have run it to update your path, you can run the perl utility.

Alternatively, you can allow all users on the system to access perl from a standard location by adding a link to perl in the /usr/bin directory. Figure 22.1 shows how to create the link and start perl. The v option shows the version of perl.


ln -s /QIBM/ProdData/DeveloperTools/pase/bin/perl /usr/bin/perl


perl -v


This is perl, version 5.005_03 built for aix


Copyright 1987-1999, Larry Wall


Perl may be copied only under the terms of either the Artistic


License or the GNU General Public License, which may be


found in the Perl 5.0 source kit.


Complete documentation for Perl, including FAQ lists, should be


found on this system using 'man perl' or 'perldoc perl', If


you have access to the Internet, point your browser at


http://www.perl.com/, the Perl Home Page.


Figure 22.1: Create a symbolic link to allow all users on the system access to perl from the standard location at /usr/bin/perl.

Perl is an ASCII application. Use ez to edit perl scripts in ASCII and to edit perl data files. See chapter 21 for other strategies for dealing with ASCII files in Qshell.

The Perl Command

The syntax of the perl command has two forms:


perl [options] [--]


ProgramFile arguments ...


perl [options] [-e


commands


]


[-]


arguments ...

You will use one or the other of these forms, but not both, in one command. You can write perl script (program code) either from the command line or in a text program file. Alternatively, write the perl program as a series of script files using the magic number (#!) syntax. Examples in this chapter use perl scripts.

Perl Options

Table 22.1 shows some of the more commonly used command-line options for perl.

Table 22.1: Perl Command-line Options

Option

Description

-w

Warn of possible errors. Always use this parameter.

-a

Automatically split the input lines on white space into array @F. The -a parameter is used with -n or -p.

-e

Perl commands follow on the command line instead of in a script file. Multiple -e options may be used.

-F/ pattern/

This is the pattern used for the -a option (auto split). The default is to split on white space.

-i[ extension ]

Edit files in place. If an extension is specified, make a backup copy of the file to the file extension specified.

-I directory

Add the directory given to the list of directories processed for included perl scripts and modules.

-n

Implicitly add a While (<>) loop around the script, automatically reading lines into the $_ special variable.

-p

The same as -n, but the line is automatically printed to simulate the behavior of sed.

-v

Show perl version information.


Perl Syntax

Perl is a large and complex language, so this chapter only presents highlights of it. The tables describing the language in this chapter are not complete. Instead, they focus on the most frequently used perl constructs.

Variables

All variables in perl are prefixed with a special character, depending on the treatment of the variable. Variables prefixed with a dollar sign are scalar variables (numbers or strings). Variables prefixed with an "at" sign are array values. In general, arrays are indexed by numbers starting with zero, but variables prefixed with a percent sign are associative arrays, which are indexed by strings. When indexing into an array, indicate you want the result to be a scalar value by using the dollar-sign prefix.

Like Qshell, perl uses predefined special variables to represent common information. Table 22.2 shows some of the more commonly used perl special variables and arrays.

Table 22.2: Special Variables and Arrays

Variable

Description

$_

The current input record, which typically represents one line of input. See $/ to change this behavior.

$.

The input line number of the last input record that was read.

$/

The input record separator, which controls how records are delimited for reading into the $_ variable. By default, the value is newline. You may set this to a multi-character value.

$,

The value used for the output field separator by the print operator. When multiple arguments are passed to the print operator, they are, by default, separated by commas.

$

The output record separator for the print operator.

$"

The separator that joins elements of arrays that are interpolated in strings.

$[

The index used for the first element of an array or the first character of a string. The default value is zero. You may set this to one, but beware of included library dependencies on zero-indexed arrays.

$ARGV

The name of the current file when reading from <>.

$&

The string that matched the last pattern match.

$`

The string that preceded what was matched by the last pattern match.

$'

The string that followed what was matched by the last pattern match.

$

If set to non-zero , forces a flush after every write. The default value is zero.

$1, $2, $3, etc

The strings that matched sub-expressions (parentheses groupings) of the last pattern match completed. $1 represents the group starting with the first left parenthesis, $2 the group starting with the second left parenthesis, etc.

$#array

The last index (the length) of the array named.

@ARGV

The array containing the command-line arguments for the script. $ARGV[0] contains the first argument.

@_

The array containing the parameter values passed to subroutines. @_[0] contains the first parameter passed to the subroutine.

%ENV

The associative array representing the current set of environment variables. Strings index associative arrays. The array %ENV will likely contain an entry for the HOME environment variable. Use $ENV{"HOME"} to access HOME.

Figure 22.2 shows usage patterns of perl variables, demonstrated by a simple lookup facility. Comments in the perl script explain details about individual steps.


cat lookupExample.pl


#!/usr/bin/perl -w


# These are simple variable assignments and substitutions.


$firstName = "Billy";


$lastName = "Bob";x


$number = "444-4340";


$fullNameAndNumber = "$firstName $lastName" . "at" . $number;


print "Name and number: $fullNameAndNumber
";


# Simple array assignment. Indexes 0 to 4


@names = ("Billy Bob", "Chuck", "Bubba", "Amos", "Claude");


for ($i=0; $i<$#names; $i++) {


print "Name #$i: $names[$i]
";


}


# Simple associative array of phone numbers Indexed by name.


%phoneNumbersByName = ("Billy Bob", "444-4340",


"Chuck", "444-2345",


"Bubba", "444-1111",


"Amos", "333-1119",


"Claude", "333-4340");


# List all of the keys (indexes) of the associative array.


@keys = keys(%phoneNumbersByName);


# About to output an array as a string, set the output field


# separator to a comma plus a space.


$" = ",";


print "Indexes of phone list: @keys
";


# Retrieve a phone number


$target = "Billy Bob";


if (defined $phoneNumbersByName{$target}) {


$lookup = $phoneNumbersByName{'Billy Bob'};


}


else {


$lookup = "Not found";


}


print "Lookup of phone number for $target is $lookup
";


lookupExample.pl


Name and number: Billy Bob at 444-4340


Name #0: Billy Bob


Name #1: Chuck


Name #2: Bubba


Name #3: Amos


Indexes of phone list: Amos, Bubba, Claude, Chuck, Billy Bob


Lookup of phone number for Billy Bob is 444-4340


Figure 22.2: This example perl code (plus comments) declares and uses perl variables to demonstrate a simple lookup capability using an associative array.

Operators

In addition to the traditional mathematical operators found in many languages, perl has operators for the manipulation, comparison, and construction of strings. Table 22.3 shows the more commonly used operators.

Table 22.3: Perl Operators

Operator

Description

<>

Read from standard input or the files specified in the @ARGV array.

< STDOUT >

Read from the standard file specified.

Read from the list of files specified in the @ARGV array.

Read from a FILEHANDLE that was opened with the perl open API.

+ - * / %

These are traditional addition, subtraction, multiplication, division, and modulo operators.

& ^

These are bitwise AND, OR, and XOR operators.

X

Create an array (or string) consisting of the operand on the left (which is an array or string) repeated the number of times specified by the operand on the right, for example, $nine9s = "9" x 9;

(dot)

Concatenate two strings, for example, $ fullname = $firstname . "". $lastname.

&&

These are logical OR and AND operators.

== != < > <= >=

These are numeric comparison operators: equal; not equal; less than; greater than; less than or equal; greater than or equal.

eq ne lt gt le ge

These are string comparison operators: equal; not equal; less than; greater than; less than or equal; greater than or equal.

<=>

The numeric-ordering operator returns -1 if the left operand is greater than the right operand, zero if they are equal, and one if the right operand is greater than the left operand.

Cmp

The string-ordering operator returns -1 if the left operand is greater than the right operand, zero if the operands are equal, and one if the right operand is greater than the left operand.

=~

The search operator targets the left operand with the search, substitution, or translation function in the right operand.

!~

The negated search operator targets the left operand with the search, substitution, or translation function in the right operand.

Functions

Perl provides a standard set of built-in functions for string and array manipulation. Perl also provides a large set of functions that provide interaction with and access to operating-system services. Table 22.4 shows some commonly used functions.

Table 22.4: Perl Functions

Function

Description

m/ pattern/flags

The match operator matches a pattern. Use flags to modify the match behavior. If the =~ or !~ operators are not used, the target for the match is the $_ variable.

s/ pattern/newpattern/flags

The substitution operator substitutes the replacement text (or pattern) for the matched pattern in the original. Use flags to modify the substitution. If the =~ or !~ operators are not used, the target for the substitution is the $_ variable.

tr/ list/replacementlist/flags

Somewhat similar to the substitution operator but more specialized, the translation operator translates characters found in the list to those in the replacement list. Use flags to modify the translation. If the =~ or !~ operators are not used, the target for the translation is the $_ variable.

print( file list )

The print function prints a string- or comma-separated list of strings (fields). If FILEHANDLE is not specified, the output goes to stdout.

time()

The time function returns the number of seconds since January 1, 1970. Use this as input to localtime().

localtime( time )

The localtime function converts the time returned from the time function to a nine-element array. The array contents are typically retrieved using the following notation:

($sec, $min, $ hour , $monthday, $month, $year, $weekday, $yearday, $isDST) = localtime(time());

chomp( string )

The chomp function safely removes end-of-line characters (represented by the $/ variable). If no end-of-line characters are present, the variable is unchanged. If no parameters are specified, the target is the $_ variable.

index( string, substring, offset )

The index function returns the position of a substring in the string, starting at offset. If an offset is not specified, it searches for the substring at the beginning of the string. This function returns -1 if the substring is not found.

length( expression )

The length function returns the length of the expression in characters.

rindex( string, substring, offset )

The rindex function returns the position of the last substring at or before an offset. If no offset is specified, it starts at the end of the string. This function returns -1 if the substring is not found.

substr( string, offset, length )

The substr function extracts a string of length characters starting at the offset in the original string. If no length is specified, substr returns the characters to the end of the string.

split( pattern, expression, limit )

The split function separates an expression at the occurrences of the pattern into an array of strings, and returns the array. Optionally, use the limit parameter to limit the number of array elements returned. If the expression is omitted, split the $_ special variable. If all parameters are omitted, split the $_ special variable on white space.

join( expression, list )

The join function joins a list into a single string, separated by the value of the expression. It returns the string.

pop( @array )

The pop function removes and returns the last value of the array, and decreases the length of the array by one.

push( @array, list )

The push function adds the values of the list onto the end of the array, and increases the length of the array by the length of the list.

shift( @array )

The shift function removes and returns the first value of the array, and decreases the length of the array by one. If an array is not specified, shift works on @ARGV.

unshift( @array, list )

The unshift function adds the values of list to the beginning of the array. The unshift function increases the length of the array by the length of the list.

keys( %array )

The keys function returns a normal array containing all of the keys (indexes) of the associative array.

values( %array )

The values function returns a normal array containing all of the values of the associative array.

defined

The defined function returns true if the variable passed as an argument has already been defined.

sub functionname { code; }

The sub function defines a subroutine with the specified function name.

undef

The undef function removes a variable definition.

local

The local function declares variables locally to the enclosing code block.

Use flags to modify the match and substitution functions:

  • The m flag enables a multiline match. In a multiline match, the newline character is not a special character. Match it with the character.
  • The g flag matches as many times as possible (globally).
  • The i flag matches in a case-insensitive fashion.
  • The o flag expands variables only once.

In addition to the flags supported by the match function, the substitution function accepts an additional flag, e , to interpret the replacement string as an expression.

You can also use flags to modify the translation function:

  • The c flag complements the search list.
  • The d flag deletes all characters not found in the search list.
  • The s flag "squeezes" all sequences of characters in the search list, replacing them with the single target character.

Regular Expressions

The perl language supports an extensive regular-expression language for specifying patterns. All characters match themselves except for the special characters explained in Table 22.5. Group a series of expressions into a single expression.

Table 22.5: Special Characters in Regular Expressions

Character

Description

(dot)

Match any single character, but not a newline character.

+

Match the preceding element one or more times.

?

Match the preceding element zero or one times.

*

Match the preceding element zero or more times.

{N, M}

Match the preceding element a minimum of N times, and a maximum of M times. Use {N} to match exactly N times. Use {N,} to match at least N times.

[ ]

Use the bracket grouping to match any of a group of characters. Use a group of [^ ] to negate the match.

( )

The operator is an OR operator. Match one of the individual expressions.

w

Match a single alphanumeric .

W

Match a single non-alphanumeric.



Match a single word boundary.

B

Match a single non-word boundary.

s

Match a single whitespace character.

S

Match a single non-whitespace character.

d

Match a numeric character.

D

Match a nonnumeric character.

f

Match the newline, carriage -return, formfeed, or tab characters, respectively.

1, 2, 3, etc.

Match a previously matched subexpression group. The 1 represents the group starting with the first left parenthesis, 2 the group starting with the second left parenthesis, etc. These are similar to the special variables $1, $2, $3... described in Table 22.2.


Perl Examples

The first examples in this section are constructed simply, while subsequent examples use more complex constructs. Examples for phone-number lookup, PTF status, and database access are repeated in C, Java, and perl, for comparison purposes. The data for all of the exercises is the goodoleboys.txt file, which was shown in the previous chapter, in Figure 21.1.

Figure 22.3 demonstrates how to use a command in the perl language on the command line, with the e option. The match operator implicitly matches the current input line. The n option implicitly loops the script around all standard input.


perl -wne 'if (m/444/) { print "$_"; } ' < goodoleboys.txt


Chuck Dec 25 444-2345 Blue Mary Sue 12 .50


Bubba Oct 13 444-1111 Buck Mary Jean 12


Billy Bob June 11 444-4340 Leotis Lisa Sue 12


Otis Sept 17 444-8000 Ol' Sal Sally 12


Roscoe Feb 2 444-2234 Rover Alice Jean 410


Arlis June 19 444-1314 Redeye Suzy Beth 12 .75


Figure 22.3: This example searches for the string 444 in the input. Use the -e option to write perl program code on the command line. The -n option loops the program over all lines in the input.

Where Figure 22.3 uses the -n operator, Figure 22.4 uses the <> operator. This example explicitly iterates through all lines of standard input. The <> operator sets the $_ variable to the input line, and returns true if there are still lines remaining in the input. The chomp function removes the newline from the input stream, requiring you to add it again if you print the $_ variable.


cat showLocalBoys.pl


#!/usr/bin/perl -w


while (<>) {


chomp;


if (m/444-/) {


print "line $.: $_
";


}


}


showLocalBoys.pl < goodoleboys.txt


line 3: Chuck Dec 25 444-2345 Blue Mary Sue 12 .50


line 4: Bubba Oct 13 444-1111 Buck Mary Jean 12


line 5: Billy Bob June 11 444-4340 Leotis Lisa Sue 12


line 7: Otis Sept 17 444-8000 Ol' Sal Sally 12


line 9: Roscoe Feb 2 444-2234 Rover Alice Jean 410


line 10: Arlis June 19 444-1314 Redeye Suzy Beth 12 .75


Figure 22.4: Use Qshell to run this perl script, which shows all records in the input file that match a local dialing prefix.

In Figure 22.5, the match function tells perl to search for strings that have the format of a telephone number. For a more explicit match, the match expression includes word boundaries ( b ) around the telephone number. The match specifically matches three occurrences of the 4 character, a dash, and four occurrences of any numeric character ( d ).


cat showLocalBoyDialList.pl


#!/usr/bin/perl -nw


chomp;


if (m/(4{3}-d{4})/) {


$name = substr($_, 0, 10);


$phone = ;


print "$name	$phone
";


}


showLocalBoyDialList.pl goodoleboys.txt

Chuck 444-2345
Bubba 444-1111
Billy Bob 444-4340
Otis 444-8000
Roscoe 444-2234
Arlis 444-1314


Figure 22.5: This perl example uses a complex regular expression to match a phone-number format. It uses the $1 variable to retrieve the previously matched sub-expression group from the match function.

Enclosing the entire phone number inside parentheses creates a sub-expression. The special variable $1 holds the value of the first sub-expression after a match. If the match function returns true, the substr() function removes the first 10 characters and assigns them to the name variable. The script then prints out the name of the phone number's owner and uses the special $1 variable to print out the number.

In Figure 22.6, telephone numbers that end in 2300 through 9999 in local exchange 444 are updated to be part of a new local exchange, 445.


cat newLocalPrefix.pl


#!/usr/bin/perl -nwei.backup


chomp;


if (m/(4{3}-(d{4}))/) {


$last4phone = ;


if ( >= 2300) {


s/(4{3}-(d{4}))/445-$last4phone/;


print STDERR "Updating 444-$last4phone
";


}


}


print "$_
";


newLocalPrefix.pl goodoleboys.txt


Updating 444-2345


Updating 444-4340


Updating 444-8000


ls good*


goodoleboys.txt goodoleboys.txt.backup


cat goodoleboys.txt


Name Born Phone Dog Wife Shotgun Paid


========= ======== ======== ======== ========= ======= =====


Chuck Dec 25 445-2345 Blue Mary Sue 12 .50


Bubba Oct 13 444-1111 Buck Mary Jean 12


Billy Bob June 11 445-4340 Leotis Lisa Sue 12


Amos Jan 4 333-1119 Amos Abigail 20


Otis Sept 17 445-8000 Ol' Sal Sally 12


Claude May 31 333-4340 Blue Etheline 12


Roscoe Feb 2 444-2234 Rover Alice Jean 410


Arlis June 19 444-1314 Redeye Suzy Beth 12 .75


Junior April 30 BR-549 Percival Lilly Faye 12


Bill Feb 29 333-4444 Daisy Daisy 20


Ernest T. ?? none none none none


Figure 22.6: This perl script updates a phone list using the -i option to perform an in-place edit with a backup.

Always use a backup file extension with the i parameter. It is very easy to make mistakes, and if you tell it to, perl with gladly throw away your original data and leave you with the corrupted data remnants resulting from a buggy script. The i parameter is used to update the input files in place. Backup files are created with a .backup extension. Perl uses all text output to the stdout file handle as replacement for the lines in the original file. Text output to the stderr file handle is not assumed to be part of the edited file.

This example demonstrates the ability to interchange strings and numeric values. The special variable $2 receives the four final digits of the telephone number. That value is used in a numeric comparison with 2300. If the value is greater than or equal to 2300, the substitution function changes the exchange to 445. The script prints a status message to stderr.

Building on the previous examples, Figure 22.7 uses the data file from Figure 22.6 to demonstrate a functioning, interactive phone-number lookup application. The application uses two associative arrays to provide lookup services based on the data file. Compare and contrast this perl application to the similar Java example in Figure 23.6 and C example in Figure 24.5. From a perl perspective, the associative array provides exactly the right functionality for a lookup program of this type. The robust and flexible regular expressions that perl provides are only used slightly in this example because the data file is composed of fixed-length fields. If the fields were delimited or needed some additional processing, the regular expression capabilities would make perl a much more attractive solution for this program.


cat phoneList.pl


#!/usr/bin/perl -w


if ($#ARGV < 0 $ARGV[0] eq '-h') {


print "Usage: phoneList [-h] ...
";


exit(1);


}


# An associative array that allows lookup of the phone number


# by the good ole boy's name


%numberByOleBoy = ();


# An associative array that allows lookup of the good ole boy


# by his wife's name.


%oleBoyByWife = ();


# Read input from all the data files passed on the command line


while () {


chomp;


if ($. == 1 $. == 2) {


# The first 2 lines of each data file represent


# header lines.


next; # Go to the next input line.


}


# For each field:


# - Take the characters from the correct column for the field


# into a variable.


# - Remove any trailing spaces at the end of the variable


$oleboy = substr($_, 0, 10);

$oleboy =~ s/s+$//g;

$oleboyswife = substr($_, 37, 10);


$oleboyswife =~ s/s+//g;


$phonenumber = substr($_, 19, 8);


$phonenumber =~ s/s+//g;


# Build an associative array so that we can lookup phone


# number based on the ole boy's name.


$numberByOleBoy{$oleboy} = $phonenumber;


# Build an associative array so that we can lookup the


# ole boy's name based on the wife's name.


if ($oleboyswife ne "none") {


$oleBoyByWife{$oleboyswife} = $oleboy;


}


}


# Set the output to be unbuffered.


$ = 1;


# Get the user's input.


print "Enter 'exit' or a name to lookup:
";


while (<>) {


chomp;


if ($_ eq "exit" $_ eq "quit") {


last;


}


# Is the name a good ole boy?


if (defined $numberByOleBoy{$_}) {


# Yes, print out the number.


print "Found good ole boy's number at $numberByOleBoy{$_}
";


}


# Otherwise, is the name a good ole boy's wife?


elsif (defined $oleBoyByWife{$_}) {


# Yes, print out the number.


print "Found good ole boy's number using his wife at


$numberByOleBoy{$oleBoyByWife{$_}}
";


}


else {


print "Didn't find number (the lookup is case sensitive)
";


}


print "Enter 'exit' or a name to lookup:
";


}


phoneList.pl goodoleboys.txt


Enter 'exit' or a name to lookup:


Bill


Found good ole boy's number at 333-4444


Enter 'exit' or a name to lookup:


Daisy


Found good ole boy's number using his wife at 333-4444


Enter 'exit' or a name to lookup:


Claude


Found good ole boy's number at 333-4340


Enter 'exit' or a name to lookup:


Etheline


Found good ole boy's number using his wife at 333-4340


Enter 'exit' or a name to lookup:


Fred


Didn't find number (the lookup is case sensitive)


Enter 'exit' or a name to lookup:


exit


Figure 22.7: This example shows a functioning, interactive phone-number lookup interface.

When developing perl programs that interact with Qshell, you can use Qshell utilities to perform tasks while processing input or output for the utilities with perl. Interacting with Qshell commands in this fashion lets you reuse the broad set of utilities for their functions.

Figure 22.8 shows a simple version of running Qshell commands and processing their output from perl. Since perl is a PASE utility, the PASE qsh utility is used to execute a Qshell command.


cat qshellFromPerl.pl


#!/usr/bin/perl -w


if ($#ARGV != 0 $ARGV[0] eq "-h") {


print "Usage: qshellFromPerl [-h] 
";


print "Run a qshell command using PASE perl utility
";


exit(1);


}


# Create a file handle connected to the output


# of a Qshell process


# A first character of "" would be used to create


# a file handle that could be written to, in order


# to send input to the created process.


open(QSH, "qsh -c "$ARGV[0]" ")


die "Couldn't open the Qshell command";


while () {


chomp;


print "QSHOUT: $_
";


}


exit(0);


qshellFromPerl.pl "ls -S"


QSHOUT: 819 lookupExample.pl


QSHOUT: 819 newLocalPrefix.pl


QSHOUT: 819 phoneList.pl


QSHOUT: 819 phoneListDB.pl


QSHOUT: 819 ptfStatus.pl


QSHOUT: 819 qshellFromPerl.pl


QSHOUT: 819 showLocalBoyDialList.pl


QSHOUT: 819 showLocalBoys.pl


Figure 22.8: Use the perl utility to process the output from any Qshell utility. Process the output in whichever way is appropriate.

Building on the ability to invoke a Qshell command, Figure 22.9 uses the Qshell system utility to interact directly with a CL command. Invoking the system utility like this is a shortcut to processing that may use a temporary file to hold the output from a Qshell or CL command or utility.


cat ptfStatus.pl


#!/usr/bin/perl -w


if ($#ARGV < 0 $ARGV[0] eq "-h") {


print "Usage: ptfStatus [-h] 
";


print "Query the status of a list of PTFs
";


exit(1);


}


$debug = 0;


# Create a file handle connected to the output


# of a process running the system command to process


# the CL command DSPPTF.


open(DSPPTF, 'system "DSPPTF OUTPUT(*PRINT)" ')


die "Couldn't open DSPPTF command";


while () {


chomp;


# PTF list in the output is a 7 character name,


# 2 alpha, 5 digits or


# 3 alpha, 4 digits


# prefixed by one space on each line.


print "<$_>
" if $debug;


if (m/^s((D{2}d{5})(D{3}d{4}))s/) {


# Use the PTF that we just matched in the parenthesis


$ptf = "";


# Grab the PTF status from the line.


$status = substr($_, 13, 19);


# Remove trailing whitespace from status.


$status =~ s/s*$//g;


$ptfList{$ptf} = $status;


print "OUT:$ptf $status
" if $debug;


}


}


print "-------	--------------------
";


print "PTF 	 Status 
";


print "-------	--------------------
";


for ($i=0; $i<=$#ARGV; $i++) {


$ptf = $ARGV[$i];


if (defined $ptfList{$ptf}) {


print "$ptf	$ptfList{$ptf}
";


}


else {


print "$ptf	Not Loaded
";


}


}


exit(0);


ptfStatus.pl SI06971 SI06972 SI06973 SI06974 SI06975 SI06976 SI06977


------- --------------------


PTF Status


------- --------------------


SI06971 Temporarily applied


SI06972 Superseded


SI06973 Not Loaded


SI06974 Not Loaded


SI06975 Temporarily applied


SI06976 Temporarily applied


SI06977 Superseded


Figure 22.9: This perl example uses the system utility to run a CL command, and then processes the output.

When running CL commands, the system utility processes temporary spooled files and job-log data created by the command.

In the case of a native Qshell command, no temporary file is created. The APIs read or write directly to the running application via an interprocess communication mechanism called a pipe . As the program runs, it runs at the same time as the started application, reading data from or writing it to the pipe. The pipe buffers the data as appropriate, but there is never a single complete copy of all of the data.

Compare and contrast the perl code in Figure 22.9 to the Java example in Figure 23.8 and the C example in Figure 24.7. The advanced functions available with perl regular expressions start to become more important in this example, enabling us to easily pick out the PTF number from the data stream that is produced by the Qshell command. Very little programming is needed to start and process the output from a Qshell utility; it almost happens naturally.

Since perl is a PASE application, the PASE system utility is executed in this example, not the Qshell system utility. The PASE and Qshell system utilities both work similarly. Use the PASE utility qsh to execute a Qshell utility from within perl (or other PASE applications). The output from the CL command is processed into an associative array. The associative array serves as the lookup mechanism for a list of randomly selected PTFs (Program Temporary Fixes).

The perl language provides a standard way to access a database using the perl DBI module. Provided with the perl implementation on iSeries is the DB2 implementation of perl database (DBI) access. Figure 22.10 demonstrates a more realistic phone-number lookup application than the example shown in Figure 22.7. The names and phone numbers reside in the relational database on the iSeries. Compare and contrast this perl database example to the Java example in Figure 23.8 and the C example in Figure 24.8.


cat phoneListDB.pl


#!/usr/bin/perl -w


use DBI;


use DBD::DB2;


use DBD::DB2::Constants;


if (defined $ARGV[0]) {


print "Usage: phoneList [-h]
";


exit(1);


}


# Create the database connection and the statement to use.


$hdbc = DBI->connect("dbi:DB2:*LOCAL") die "Couldn't connect";


$ps = $hdbc->prepare("SELECT PHONENUMBER FROM QSHELLDATA.CUTOMERS " .


"WHERE NAME = ? OR WIFE = ?") die "Couldn't


prepare, err=$hdbc->err";


# Set the output to be unbuffered.


$ = 1;


# Get the user's input.


print "Enter 'exit' or a name to lookup:
";


while (<>) {


chomp;


if ($_ eq "exit" $_ eq "quit") {


last;


}


# Set the input parameters


$ps->bind_param(1, $_);


$ps->bind_param(2, $_);


$ps->execute() warn "Couldn't execute, err=$hdbc->err";


# retrieve the first row.


@row = $ps->fetchrow;


if (!defined $row[0]) {


print STDERR "Didn't find customer: $_
";


}


else {


print STDOUT "Found $_ at $row[0]
";


}


$ps->finish();


print "Enter 'exit' or a name to lookup:
";


}


$hdbc->disconnect();


exit(0);


phoneListDB.pl


Enter 'exit' or a name to lookup:


Bill


Found Bill at 333-4444


Enter 'exit' or a name to lookup:


Daisy


Found Daisy at 333-4444


Enter 'exit' or a name to lookup:


Claude


Found Claude at 333-4340


Enter 'exit' or a name to lookup:


Etheline


Found Etheline at 333-4340


Enter 'exit' or a name to lookup:


Fred


Didn't find customer: Fred


Enter 'exit' or a name to lookup:


exit


Figure 22.10: Use perl to access the iSeries database. The additional modules for database access are provided with the implementation of perl. This example does the phone-number lookup demonstrated in Figure 22.7, but uses the database for input, instead of a text file.

Using the perl operator along with the die or warn function lets a concise error-handling model take shape in this program. The database functions used by this program are designed to be similar to the Java and C models, which helps developers who program in multiple languages. The strength of automatic memory-management and automatic conversion of data types shows here. The program doesn't need to concern itself about the size or type of data parameters, or with allocating storage for them.


Summary

The perl language provides a powerful text-processing environment. You can use perl to access Qshell and iSeries services, creating simple yet powerful scripts or applications.






QShell for iSeries
Qshell for iSeries
ISBN: 1583470468
EAN: 2147483647
Year: 2003
Pages: 219
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