How To Properly Specify Command and Arguments to Exec in Perl

Author: erics, December 11th, 2019

When using Perl’s exec() call, the best way to invoke it is as follows:

exec("$dir/myprog.sh",@ARGV);

1	exec("$dir/myprog.sh",@ARGV);

This syntax does some important things: – passes a scalar value as the first argument which exec interprets as PROGRAM – passes an array as the second argument which exec will use as the arguments to pass into PROGRAM Note […]

Categories: How-To's, Technology Tags: Arg, Args, Argument, Arguments, bash, Exec, Execute, perl, Program, sh, Shell, System | No comments

How To Read Multiple Lines of User Input from the Command Line in Perl

Author: erics, October 9th, 2019

Use Case: Export Apple Reminders from MacOS application to cleaned plain text, i.e. remove unwanted spaces, blank lines and square brackets PROCEDURE Click on a single item in the MacOS Reminders app list Select All (either Command-a or use Edit->Select All) Copy (either Command-c or use Edit->Copy) Open Terminal Run cleanme Paste the copied reminders […]

Categories: How-To's, Technology Tags: apple, array, input, List, MacOS, Multi, Multi-line, Multiline, Multiple, perl, Plain, Plaintext, Read, Reminders, STDIN, Terminal, text() | No comments

How To Enable Variable References in Perl While Using Strict

Author: erics, August 4th, 2019

I wanted to call a sub-routine based on a variable in Perl, like this:

our $role = 'master';
&$role;

1 2	our $role = 'master'; &$role;

but it failed because of use strict:

Can't use string ("master") as a subroutine ref while "strict refs" in use at /opt/continuent/tungsten/tools/tungsten_find_orphaned line 213.

1	Can't use string ("master") as a subroutine ref while "strict refs" in use at /opt/continuent/tungsten/tools/tungsten_find_orphaned line 213.

To enable using a variable as a reference, simply specify that to Perl:

use strict
no strict "refs";

1 2	use strict no strict "refs";

Categories: How-To's, Technology Tags: de-reference, dereference, howto, no strict, perl, Reference, Strict, Subroutine, tips, Variable | No comments

How To Install/Update CPAN on MacOS Mojave with fatal error: ‘EXTERN.h’ file not found

Author: erics, June 12th, 2019

The Problem Tried to install the latest version of cpan and got stuck. Tracked it down to the dependency module Mac::SystemDirectory which was failing to build:

cpan[1]> install Mac::SystemDirectory                                                                                                                                                                                                                                                    
Reading '/var/root/.cpan/Metadata'
  Database was generated on Sun, 09 Jun 2019 07:17:02 GMT
Running install for module 'Mac::SystemDirectory'
Running make for E/ET/ETHER/Mac-SystemDirectory-0.10.tar.gz
Checksum for /var/root/.cpan/sources/authors/id/E/ET/ETHER/Mac-SystemDirectory-0.10.tar.gz ok
Scanning cache /var/root/.cpan/build for sizes
............................................................................DONE

  CPAN.pm: Building E/ET/ETHER/Mac-SystemDirectory-0.10.tar.gz

HASCOMPILEREZFt/TESTUSSI.c:2:10: fatal error: 'EXTERN.h' file not found
#include "EXTERN.h"
         ^~~~~~~~~~
1 error generated.
Couldn't execute cc  -g -pipe -fno-common -DPERL_DARWIN -fno-strict-aliasing -fstack-protector -Os "-I/System/Library/Perl/5.18/darwin-thread-multi-2level/CORE"   -c HASCOMPILEREZFt/TESTUSSI.c -o HASCOMPILEREZFt/TESTUSSI.o: Inappropriate ioctl for device at Makefile.PL line 14.
Requires a compiler
Warning: No success on command[/usr/bin/perl Makefile.PL INC=-I/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/System/Library/Perl/5.18/darwin-thread-multi-2level/CORE]
  ETHER/Mac-SystemDirectory-0.10.tar.gz
  /usr/bin/perl Makefile.PL INC=-I/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/System/Library/Perl/5.18/darwin-thread-multi-2level/CORE -- NOT OK
Running make test
  Make had some problems, won't test
Running make install
  Make had some problems, won't install
Failed during this command:
 ETHER/Mac-SystemDirectory-0.10.tar.gz        : writemakefile NO '/usr/bin/perl Makefile.PL INC=-I/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/System/Library/Perl/5.18/darwin-thread-multi-2level/CORE' returned status 6400

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cpan[1]> install Mac::SystemDirectory

Reading '/var/root/.cpan/Metadata'

Database was generated on Sun, 09 Jun 2019 07:17:02 GMT

Running install for module 'Mac::SystemDirectory'

Running make for E/ET/ETHER/Mac-SystemDirectory-0.10.tar.gz

Checksum for /var/root/.cpan/sources/authors/id/E/ET/ETHER/Mac-SystemDirectory-0.10.tar.gz ok

Scanning cache /var/root/.cpan/build for sizes

............................................................................DONE

CPAN.pm: Building E/ET/ETHER/Mac-SystemDirectory-0.10.tar.gz

HASCOMPILEREZFt/TESTUSSI.c:2:10: fatal error: 'EXTERN.h' file not found

#include "EXTERN.h"

^~~~~~~~~~

1 error generated.

Couldn't execute cc -g -pipe -fno-common -DPERL_DARWIN -fno-strict-aliasing -fstack-protector -Os "-I/System/Library/Perl/5.18/darwin-thread-multi-2level/CORE" -c HASCOMPILEREZFt/TESTUSSI.c -o HASCOMPILEREZFt/TESTUSSI.o: Inappropriate ioctl for device at Makefile.PL line 14.

Requires a compiler

Warning: No success on command[/usr/bin/perl Makefile.PL INC=-I/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/System/Library/Perl/5.18/darwin-thread-multi-2level/CORE]

ETHER/Mac-SystemDirectory-0.10.tar.gz

/usr/bin/perl Makefile.PL INC=-I/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/System/Library/Perl/5.18/darwin-thread-multi-2level/CORE -- NOT OK

Running make test

Make had some problems, won't test

Running make install

Make had some problems, won't install

Failed during this command:

ETHER/Mac-SystemDirectory-0.10.tar.gz : writemakefile NO '/usr/bin/perl Makefile.PL INC=-I/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/System/Library/Perl/5.18/darwin-thread-multi-2level/CORE' returned status 6400

The Solution Use the MacOS installer command to deploy the needed files:

xcode-select --install
sudo installer -pkg /Library/Developer/CommandLineTools/Packages/macOS_SDK_headers_for_macOS_10.14.pkg -target /
installer: Package name is macOS_SDK_headers_for_macOS_10.14
installer: Installing at base path /
installer: The install was successful.

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xcode-select --install

sudo installer -pkg /Library/Developer/CommandLineTools/Packages/macOS_SDK_headers_for_macOS_10.14.pkg -target /

installer: Package name is macOS_SDK_headers_for_macOS_10.14

installer: Installing at base path /

installer: The install was successful.

The, rerunning the cpan install works:

cpan[1]> install Mac::SystemDirectory                                                                                                                                                                                                                                                    
...
Running make install
Files found in blib/arch: installing files in blib/lib into architecture dependent library tree
Installing /Library/Perl/5.18/darwin-thread-multi-2level/auto/Mac/SystemDirectory/SystemDirectory.bs
Installing /Library/Perl/5.18/darwin-thread-multi-2level/auto/Mac/SystemDirectory/SystemDirectory.bundle
Installing /Library/Perl/5.18/darwin-thread-multi-2level/Mac/SystemDirectory.pm
Installing /usr/local/share/man/man3/Mac::SystemDirectory.3pm
Appending installation info to /Library/Perl/Updates/5.18.2/darwin-thread-multi-2level/perllocal.pod
  ETHER/Mac-SystemDirectory-0.10.tar.gz
  /usr/bin/make install  -- OK

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cpan[1]> install Mac::SystemDirectory

...

Running make install

Files found in blib/arch: installing files in blib/lib into architecture dependent library tree

Installing /Library/Perl/5.18/darwin-thread-multi-2level/auto/Mac/SystemDirectory/SystemDirectory.bs

Installing /Library/Perl/5.18/darwin-thread-multi-2level/auto/Mac/SystemDirectory/SystemDirectory.bundle

Installing /Library/Perl/5.18/darwin-thread-multi-2level/Mac/SystemDirectory.pm

Installing /usr/local/share/man/man3/Mac::SystemDirectory.3pm

Appending installation info to /Library/Perl/Updates/5.18.2/darwin-thread-multi-2level/perllocal.pod

ETHER/Mac-SystemDirectory-0.10.tar.gz

/usr/bin/make install -- OK

Categories: How-To's, Technology Tags: 10.14, CPAN, Error, extern.h, Fatal, Fatal Error, File not found, Header, headers, howto, Install, installer, Libraries, Library, MacOS, Mojave, not found, Package, perl, pkg, System, tips, update, upgrade, XCode | No comments

How To Use Regex Negative Lookahead To Exclude Strings

Author: erics, May 31st, 2019

I have a task in Perl to list specific files based on pattern match, those with and those without the string “_from_”. There are two files in the directory to filter: static-east.properties static-east_from_west.properties To capture the files with the _from_ string was easy:

/^static-(.*?)_from_(.*?)\.properties$/

1	/^static-(.?)_from_(.?)\.properties$/

To capture the files WITHOUT the _from_ string was not quite […]

Categories: How-To's, Technology Tags: exclude, howto, Lookahead, Negative, Negative Lookahead, perl, Regex, tips, without | No comments

How To Reformat or Re-indent Files in VIM

Author: erics, January 11th, 2019

In the normal vim mode, typing gg=G will reindent the entire file. == will re-indent just the current line. http://vim.wikia.com/wiki/Fix_indentation

Categories: How-To's, Technology Tags: Auto-indent, Format, howto, Indent, perl, re-indent, Reformat, tips, vi, vim | No comments

How To Calculate Dates In Perl Using Date::Manip

Author: erics, September 18th, 2017

my $created_at  = '2017-09-18T13:43:40Z';
my $marker      = DateCalc('today','30 days ago');
my $cmp = Date_Cmp($created_at,$marker);
if ($cmp < 0) { print "Older than marker!\n"; } else { print "Same date or later than marker\n"; }

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my $created_at = '2017-09-18T13:43:40Z';

my $marker = DateCalc('today','30 days ago');

my $cmp = Date_Cmp($created_at,$marker);

if ($cmp < 0) { print "Older than marker!\n"; } else { print "Same date or later than marker\n"; }

Categories: How-To's, Technology Tags: Calc, Date, Date::Manip, Delta, howto, perl, tips | No comments

How To Watch https Calls to Apache 2.4 using Perl and mod_status

Author: erics, September 5th, 2017

Step 1: Enable Apache status and lock it down: Make sure mod_status is being loaded:

shell> grep -Rn mod_status /etc/httpd/*

/etc/httpd/conf.modules.d/00-base.conf:58:LoadModule status_module modules/mod_status.so

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shell> grep -Rn mod_status /etc/httpd/*

/etc/httpd/conf.modules.d/00-base.conf:58:LoadModule status_module modules/mod_status.so

Add support for the call just under the first DocumentRoot statement:

shell> vim /etc/httpd/conf/httpd.conf

<Location /server-status>
    SetHandler server-status
    Require ip 127.0.0.1
    Require ip ::1
    Require ip {Your_IP_Here}
</Location>

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shell> vim /etc/httpd/conf/httpd.conf

SetHandler server-status

Require ip 127.0.0.1

Require ip ::1

Require ip {Your_IP_Here}

</Location>

Step 2. Prepare your environment:

shell> cpan YAML HTML::TableExtract

1	shell> cpan YAML HTML::TableExtract

Step 3: Create and run the status script: (See the astat contents at the bottom)

shell> vim /root/astat
shell> chmod 755 /root/astat
shell> vi ~/.bashrc

ADD: alias ipw='while true; do sleep 5; /root/astat; done'

shell> ipw

1.2.3.4|yourdomain.com:443|POST /wp-cron.php?doing_wp_cron=1563901063.57946491241455078125|

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shell> vim /root/astat

shell> chmod 755 /root/astat

shell> vi ~/.bashrc

ADD: alias ipw='while true; do sleep 5; /root/astat; done'

shell> ipw

1.2.3.4|yourdomain.com:443|POST /wp-cron.php?doing_wp_cron=1563901063.57946491241455078125|

/root/astat

#!/usr/bin/perl

use strict;

use HTML::TableExtract;

# PATH to "curl" utility
my $CURL = "/usr/bin/curl";

# URL of the server-status we want to process
my $STATUS_URL = "http://localhost/server-status";

# those are the headers in the first row of the table we want to extract
# Used by HTML::TableExtract to search for our table, within the whole HTML output
my $headers =['Srv','PID','Acc','M','CPU','SS','Req','Conn','Child','Slot','Client','VHost','Request'];

# Let's fetch the status page...
my $output = `$CURL -s $STATUS_URL`;

# Let's search for our table within the HTML...
my $tables = HTML::TableExtract->new( headers => $headers );

# We found it (hopefully), so let's parse it...
$tables->parse($output);

# ...and let's stick to the first one
my $status_table = $tables->first_table_found;

# Now let's loop allover the rows...
foreach my $row_ref ($status_table->rows) {
      # Let's de-reference the ARRAY reference, so to better manager
      # the various elements...
      my @row = @$row_ref;

      # Let's check for IP
      next if $row[10]=~/127.0.0.1/;
      next if $row[10]=~/216.66.125.161/;
      next if $row[10]=~/69.162.124.235/;

      # Let's check for an OPTIONS row...
      if ($row[12]=~/OPTIONS/) {
         # simply skip to next row in the loop
         next;
      }

      # Let's choose whatever columns we want (first column has index "0")
      # So here we have Srv, PID, Client and Request
      #foreach my $column (0,1,10,12) {
      foreach my $column (10,11,12) {
        print $row[$column]."|";
      }
      print "\n";
}

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#!/usr/bin/perl

use strict;

use HTML::TableExtract;

# PATH to "curl" utility

my $CURL = "/usr/bin/curl";

# URL of the server-status we want to process

my $STATUS_URL = "http://localhost/server-status";

# those are the headers in the first row of the table we want to extract

# Used by HTML::TableExtract to search for our table, within the whole HTML output

my $headers =['Srv','PID','Acc','M','CPU','SS','Req','Conn','Child','Slot','Client','VHost','Request'];

# Let's fetch the status page...

my $output = `$CURL -s $STATUS_URL`;

# Let's search for our table within the HTML...

my $tables = HTML::TableExtract->new( headers => $headers );

# We found it (hopefully), so let's parse it...

$tables->parse($output);

# ...and let's stick to the first one

my $status_table = $tables->first_table_found;

# Now let's loop allover the rows...

foreach my $row_ref ($status_table->rows) {

# Let's de-reference the ARRAY reference, so to better manager

# the various elements...

my @row = @$row_ref;

# Let's check for IP

next if $row[10]=~/127.0.0.1/;

next if $row[10]=~/216.66.125.161/;

next if $row[10]=~/69.162.124.235/;

# Let's check for an OPTIONS row...

if ($row[12]=~/OPTIONS/) {

# simply skip to next row in the loop

next;

}

# Let's choose whatever columns we want (first column has index "0")

# So here we have Srv, PID, Client and Request

#foreach my $column (0,1,10,12) {

foreach my $column (10,11,12) {

print $row[$column]."|";

}

print "\n";

}

Categories: How-To's, Technology Tags: 2.4, apache, Apache 2.4, CPAN, howto, http, httpd, https, mod_status, perl, Status, tips, YAML | No comments

How To Batch Search and Replace Multiple Files Using PERL

Author: erics, October 16th, 2014

Using PERL, we can easily do a search and replace across multiple files. perl -pi -w -e ‘s/SEARCH_FOR/REPLACE_WITH/g;’ FILE_LIST The following example will replace all occurrences of “hello” with “goodbye” inside files ending with .txt:

perl -pi -w -e 's/hello/goodbye/g;' *.txt

1	perl -pi -w -e 's/hello/goodbye/g;' *.txt

To handle special characters, use the hex value. For example, to convert MS web files that use control characters: […]

Categories: How-To's, Technology Tags: Batch, howto, perl, Replace, search, tips | No comments

How To Force Getopt::Long To Be Case Sensitive in Perl

Author: erics, March 19th, 2014

use Getopt::Long qw(:config no_ignore_case);

1	use Getopt::Long qw(:config no_ignore_case);

Categories: How-To's, Technology Tags: Arg, Args, Case, Case sensitive, cli, Getopt, Getopt::Long, howto, no_ignore_case, option, perl, Sensitive, tips | No comments

How To Properly Specify Command and Arguments to Exec in Perl

How To Read Multiple Lines of User Input from the Command Line in Perl

How To Enable Variable References in Perl While Using Strict

How To Install/Update CPAN on MacOS Mojave with fatal error: ‘EXTERN.h’ file not found

How To Use Regex Negative Lookahead To Exclude Strings

How To Reformat or Re-indent Files in VIM

How To Calculate Dates In Perl Using Date::Manip

How To Watch https Calls to Apache 2.4 using Perl and mod_status

How To Batch Search and Replace Multiple Files Using PERL

How To Force Getopt::Long To Be Case Sensitive in Perl

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