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Command-line arguments to command-line Perl

by RecursionBane (Acolyte)
on Oct 03, 2010 at 20:04 UTC ( #863203=perlquestion: print w/ replies, xml ) Need Help??
RecursionBane has asked for the wisdom of the Perl Monks concerning the following question:

Greetings, Monks!

Long have I assimilated knowledge from you, unseen. I emerge from the shadows of Lurkwood to place this query before you:

How do I provide command-line arguments to a command-line Perl call (from a tcsh script, no less)?

The purpose of this operation is to replace this line in ConfigFile:

'def' => '',

With this:

'def' => 'dumper/$tcsh_input',

(Where $tcsh_input is actually a command-line argument to the tcsh script)

Here is what I am attempting now in my tcsh script:

perl -pi -e '$design = $ARGV[0] ; s/.*'def'.*''/\t"def" => "dumper\/$design.def",/g' ConfigFile $tcsh_input

Any arguments after the -e switch, however, seem to be treated as input files, so I see this:

>> perl -pi -e '$design = $ARGV[0] ; s/.*'def'.*''/\t"def" => "dumper +\/$design.def",/g' ConfigFile ADCIF Can't open ADCIF: No such file or directory, <> line 194.

Is there a separate switch I can use before -e to represent the arguments (accessible through @ARGV) to the program?

Kindly bless me with your wisdom, so that I may express my gratitude and scurry back into the shadows from whence I came; all this light is hurting my eyes.

~Recursion

Comment on Command-line arguments to command-line Perl
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Re: Command-line arguments to command-line Perl
by NetWallah (Abbot) on Oct 03, 2010 at 20:35 UTC
    Your shell is messing with the quote characters.

    THis looks like linux, since you use single quotes after the -e.

    In this case, you need to escape (for the shell) every other single quote till the end of the argument.

    What I usually do to avoid the isue is to use "qq" or "q" to qote the pieces that need quoting.

         Syntactic sugar causes cancer of the semicolon.        --Alan Perlis

      Thanks for the response, NetWallah!

      This is, indeed, Linux. Rather than escape-character woes, I think the problem I'm facing is because everything after the -e <program code> switch is treated as an input file (and not an argument to the Perl program itself).

      In my code example, I would like $ARGV[0] to contain a certain value (ADCIF, in this case):

      perl -pi -e '$design = $ARGV[0] ; s/.*'def'.*''/\t"def" => "dumper\/$design.def",/g' ConfigFile $tcsh_input

      This code should behave like so:

      perl -pi -e '$design = "ADCIF" ; s/.*'def'.*''/\t"def" => "dumper\/$design.def",/g' ConfigFile

      Here, I am trying to provide "ADCIF" to the perl script on-the-fly (which is why I need the argument to be contained in @ARGV).

      I apologize if my initial question was unclear. Please let me know if you have any other suggestions.

      ~RecursionBane

        I think you don't really understand what -p does.

        I recommend that you read about it in "perldoc perlrun".

        In your example you seem to expect that "ConfigFile" is treated as the name of the file that -p workes on and all the other command-line arguments go to @ARGV.

        This is wrong.

        What happens is that ALL arguments (including "ConfigFile") go to @ARGV but then are treated (via -p's magic) as filenames. This is why you get the error.

        So you have to pass your data to perl via some other mechanism if you want to use -p (I would use an environment variable).

        This seems to be working
        cat test 1 2 3 4 5 perl -pe 'BEGIN{$prefix=pop;}s/(\d+)/$prefix.$1/' test A A.1 A.2 A.3 A.4 A.5
Re: Command-line arguments to command-line Perl
by eyepopslikeamosquito (Canon) on Oct 03, 2010 at 22:21 UTC

    I'm curious as to why you need to write a tcsh script at all. Writing scripts in csh (or tcsh) is generally frowned upon; see Csh Programming Considered Harmful for the gory details. Good old /bin/sh is more portable and a generally sounder programming language.

    If you possibly can get away with it, however, I strongly urge you to consider writing the whole thing in Perl.

      eyepopslikeamosquito, I agree with you on this point. I usually script entirely in Perl and shy away from shell scripts on principle.

      In this instance, however, it was necessary to write a one-liner for inclusion in a previously existing shell script that couldn't have dependencies on external Perl scripts. An installation of Perl, however, is guaranteed on all target systems.

      ~RecursionBane
Re: Command-line arguments to command-line Perl
by BrowserUk (Pope) on Oct 04, 2010 at 00:57 UTC

    Take a look at Perl's -s option.

    Ignoring any quoting issues, something like this should work:

    perl -pi -se 's/.*'def'.*''/\t"def" => "dumper\/$D.def",/g' -D=ADCIF C +onfigFile

    Note: That -D=... becomes $D inside the script.


    Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
    "Science is about questioning the status quo. Questioning authority".
    In the absence of evidence, opinion is indistinguishable from prejudice.

      Thanks for the suggestion, BrowserUk. I wasn't able to get this to work, because perl seemed to think that the argument was meant for it, rather than the script, and I ended up using suhailck's BEGIN() solution, instead.

      I do appreciate everyone's time and effort in helping me understand one of Perl's lesser-known functionalities! Thanks, everyone!

      ~RecursionBane

        I wasn't able to get this to work, because perl seemed to think that the argument was meant for it, rather than the script,

        Sorry. I don't often use -s with -e.

        You have to use -- to delineate between switches meant for perl, and those meant for the -e script:

        perl -pi -se's/.*'def'.*''/\t"def"=>"dumper\/$D.def",/g' -- -D=ADCIF C +onfigFile

        Not very practical on the command line, but useful in shell scripts.


        Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
        "Science is about questioning the status quo. Questioning authority".
        In the absence of evidence, opinion is indistinguishable from prejudice.

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