How can I check if a Perl module is installed on my system from the command line

Question

I tried to check if XML  Simple is installed in my system or not   perl -e  while   lt  INC gt     while   lt      pm gt     print     n          The above one-liner was used for listing all modules installed in my system  However  it is not listing XML modules   However  the following executes fine   perl -e  use XML  Simple     What might be the issue

User · Answer

If you re running ActivePerl under Windows    C   gt ppm query   to get a list of all installed modules C   gt ppm query XML-Simple to check if XML  Simple is installed

User · Answer

perl -MXML  Simple -le  print  INC  XML Simple pm     From the perlvar entry on  INC          INC         The hash  INC contains entries for each filename included via the do  require  or use operators  The key is the filename you specified  with module names converted to pathnames   and the value is the location of the file found  The require operator uses this hash to determine whether a particular file has already been included       If the file was loaded via a hook  e g  a subroutine reference  see require for a description of these hooks   this hook is by default inserted into  INC in place of a filename  Note  however  that the hook may have set the  INC entry by itself to provide some more specific info

User · Answer

If you want to quickly check if a module is installed  at least on Unix systems  with Bash as shell   add this to your  bashrc file   alias modver  perl -e  eval qq use     ARGV 0          v              ARGV 0    VERSION     print      qq No module found  n      v qq Version     v  n  qq Found   n      1    Then you can     gt  modver XML  Simple No module found    gt  modver DBI Version 1 607

User · Answer

You can check for a module s installation path by   perldoc -l XML  Simple   The problem with your one-liner is that  it is not recursively traversing directories sub-directories  Hence  you get only pragmatic module names as output

User · Answer

I believe your solution will only look in the root of each directory path contained in the  INC array   You need something recursive  like       perl -e  foreach   INC        print  find    -type f -name    pm

User · Answer

For example  to check if the DBI module is installed or not  use  perl -e  use DBI     You will see error if not installed   from http   www linuxask com

User · Answer

Quick and dirty     perl -MXML  Simple -e 1

User · Answer

Bravo for  user80168 s solution  I m still counting   s    but to avoid all the escaping involved with aliases and shells       cat   bin perlmod perl -le eval qq require  ARGV 0            print    Found  ARGV 0  Version     eval   ARGV 0 - gt VERSION           print  Not installed     1   works reasonably well    Here might be the simplest and most  modern  approach  using Module  Runtime   perl -MModule  Runtime use module -E        say   ARGV 0     use module  ARGV 0  - gt VERSION  DBI   This will give a useful error if the module is not installed   Using -MModule  Runtime requires it to be installed  it is not a core module

User · Answer

What you re doing there is not recursing into directories  It is only listing the modules in the root directory of the  INC directory   The module XML  Simple will live in one of the  INC paths under XML Simple pm   What he said above to find specific modules   CPAN explains how to find all modules here  see How to find installed modules

User · Answer

while   lt  INC     This joins the paths in  INC together in a string  separated by spaces  then calls glob   on the string  which then iterates through the space-separated components  unless there are file-globbing meta-characters    This doesn t work so well if there are paths in  INC containing spaces                   or    and there seems to be no reason to avoid the safe alternative   for   INC

[perl] How can I check if a Perl module is installed on my system from the command line?

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