use File::Which;                  # exports which()
my %paths;
$paths{rm} = which('rm');
$paths{tar} = which('tar');
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    use IPC::Cmd qw[can_run run];

    my $full_path = can_run('wget') or warn 'wget is not installed!';
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For tools that don't follow that general rule, you could use $ENV{PATH} to see if a file with a chosen name happens to exist in any of the user's current execution-path directories -- something like:

my $tool_name = "tar";  # simple example
my $tool_path = '';

for my $path ( split /:/, $ENV{PATH} ) {
    if ( -f "$path/$tool_name" && -x _ ) {
        print "$tool_name found in $path\n";
        $tool_path = "$path/$tool_name";
        last;
    }
}
die "No $tool_name command available\n" unless ( $tool_path );
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I don't know, but you might need to  split /[;:]/ if you want that to work in the "standard" windows shell as well as on unix(-like) systems.

If you promise to only use a unix-like environment (incl, cygwin or uwin on windows), you could also depend on the "which" command:

my $tool_name = "tar";
my $tool_path = `which $tool_name`;
die "No $tool_name command available\n" unless ( $tool_path );
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(Another update: D'oh -- I should have known there was a module for this!)

Hello,

Using 'which' or the path as suggested elsewhere in this thread are definitely ways to get what you want.

You could just check if the file exists and is executable:

if (-e '/bin/tar' && -x _) {
  doSmt();
}
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tar(1) and rm(1) should be in /bin on pretty much any Unix system, so you could get away without checking the path (at least for the commands you listed).

If I remember correctly, some incarnations of Unix allow executable files to be effectively unreadable, so it might be best to check for existence and "executability", and not readability.

Another way is to execute the command with an argument of --version or --help, this way you are sure the command executes. You don't need to actually provide any files or do something, such as tar'ing a directory. At least all common GNU programs should accept the version/help arguments, but try it for the specific commands you want to use.

Good luck!

Why i don't want to execute and check ? Because, i wish to check commands such as rm, tar. If i want to check the rm by executing then, i should create a temporary file and for that i should whether i have permission or not and the process goes recursive.

As suggested above, the best thing to check where the binary lives is to use one of the modules mentioned.

However, there might be situations, where the command does not exist on PATH, like shell aliasing or internal command.

I would just run the desired command with system and check for the result with $?, as described in system documentation's example.

there might be situations, where the command does not exist on PATH, like shell aliasing or internal command.

This is tricky. It is pretty system dependent on what the default shell for system is. If you know it is bash, you could shell out and do a type COMMANDNAME.
-- 
Ronald Fischer <ynnor@mm.st>