Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

Hello Monks,
I'm writing a Tk entry that emulates term:
open(COM,"$run_cmd 2>&1 |") || die "Could not execute command\n";
$_ = <COM>;
do{
$txt -> insert('end',$_);
}
while(<COM>);
close(COM);
$txt->see('end');
$txt_2->see('end');
$cmd_entry->delete('0.0', 'end');
ruuning the command "ls -l *" will work just fine
, but when Im trying to run "l" which is an alias for "ls -l *" it is not recognized. how do I pass my environment setup through the pipeline. Thanks in advance dear Monks. Michael

Replies are listed 'Best First'.
Re: passing setup via pipeline
by Corion (Patriarch) on May 25, 2010 at 07:17 UTC

    Shell aliases do not work, because system does not (always) invoke the shell. You will need to explicitly invoke the shell if you want shell aliases to work.

[reply]
      As an addition to Corion's comments, it also depends on where your alias is specified, and which shell you are using. Even if system does invoke a shell it will be a Bourne shell (/bin/sh -c). So if, for example, your aliases are defined in ~/.kshrc then that will not be read. If you invoke your shell explicitly then you should carefully note which startup files are executed for non-login non-interactive sessions. For example, Korn shell 88, Korn shell 93, and Bash all have different rules for that.

      Personally I would discourage use of aliases anywhere except as an interactive keyboard productivity aid - they are a support nightmare when used in scripts.
[reply]
      hmmm

      I was thinking to use another pipeline, for example:
      open(MYPIPE,"source .aliases|");
      my $mypipe = <MYPIPE>;
      open(COM,"$mypipe | $run_cmd 2>&1 |") || die "Could not execute command\n";

      $_ = <COM>;
      do{
      $txt -> insert('end',$_);
      }

      while(<COM>);
      close(COM);


      what do you think, does it have a chance
      BR
      Michael
[reply]
        First, 'source' is a c-shell or bash built-in, so you need to specify the shell.
        Second, that would just create the aliases in one child process. The second open will run a different process without the aliases.
[reply]

        I think you want open3 or similar. 

        open3(*TO_CHLD, *FR_CHLD, undef, 'bash')

        [download]

        Then you can print out commands to TO_CHLD and collect the output from FR_CHLD. Then you can issue shell commands including aliases, and the state of the shell (incl current work dir and environment settings) will persist between commands.

        Hum, actually, you would need a pty instead of a pipe to get interactive behaviour. IPC::Run can do all of this pretty easily, so it's probably a better choice than open3

[reply]
[d/l]
[select]

        Your idea does not make any sense to me.

[reply]
Re: passing setup via pipeline
by almut (Canon) on May 25, 2010 at 10:19 UTC

    Presuming your aliases are defined in .aliases (and in bourne shell compatible syntax), this should work: 

    my $run_cmd = 'l';

open(COM, ". .aliases\n$run_cmd 2>&1 |") || die "Could not execute com
+mand\n";
...

    [download]

    Note that there must be a newline (not a semicolon) after sourcing the .aliases file, because aliases cannot be used on the same line that they are defined.

    P.S.: not all shells will by default expand aliases, unless in interactive mode. For example, sh does, while bash does not (even if sh is just a symlink to bash), but you can explicitly enable the feature via shopt -s expand_aliases.  Hence, the above example only works because perl calls /bin/sh -c behind the scenes (at least typically — check with perl -V:sh).

[reply]
[d/l]
[select]
      Hi all,
      This is something I wanted to avoid, since it is a preaty heavy setup.
      So I don't want to run it per each command I perform.
      At any case, you've been a great help!
      Thank U monks!

      Michael - du lak
[reply]

Back to Seekers of Perl Wisdom