Re: Very Simple script driving me nuts!

From: Kevin Collins (spamtotrash_at_toomuchfiction.com)
Date: 05/16/04

  • Next message: Kevin Collins: "Re: Unix: List only File names and not directory" 
    Date: Sat, 15 May 2004 22:54:47 GMT

    In article <8bSdncQ5mL9l6TvdRVn-jw@comcast.com>, Ed Morton wrote:
    >
    >
    > Trent Curry wrote:
    >> I know I am missing something really trivial here. I've bene away from
    >> shell scripting over the years, for the most part been working with the
    >> likes of Perl, C++, and Java, and I seem to have forgotten some aspect
    >> of shell programming it seems thats biting me in the arse, when I wanted
    >> to write an utterly simple script to save me some time.
    >>
    >> sendcmd:
    >> 1 #!/bin/sh
    >> 2
    >> 3 CMD="./sendcommand blah 127.0.0.1 2701 '$*'"
    >> 4 echo -n "CMD: $*"
    >> 5 echo
    >> 6 $CMD
    >> 7 echo
    >>
    >> Say I run it like this, the echo looks fine
    >
    > No it doesn't. It'd look fine if you saw "do this" appear twice wsince
    > you're trying to include $* twice, once at line 3 and again at line 4.

    Nope - line 4 is missing the '$' from the variable named CMD! It says 'CMD' and
    it should say '$CMD'. You are right about not needing the '$*' on line 4,
    though.

    >> $ ./sendcmd do this
    >> CMD: do this
    >
    > In the above, you're seeing "do this" becau8se of the $* on line 4 of
    > your script. The '$*' at line 3 is evaluating to '' since $* isn't
    > expanded within single quotes. That same effect is causing your other
    > problems.

    That is just wrong. Any variable inside double-quotes is ALWAYS interpolated,
    regardless of single-quotes because the whole string is double-quoted. Did you
    test this? I just did with bash and sh - works as expected: all arguments are
    in a single quoted string

    >> but sendcommand ask as if no params were passed. If I remove the ''
    >> around $* on line 3, then it works, but I need literal single quotes
    >> aroudn the params being pased, so to allow spaces. I wanted to use $* so
    >> I don't have type any surrounding quotes when I use my script, and have
    >> the script put singles around that. (Notice I didnt put any '' around
    >> "do this" on the command line.
    >
    > Try this:
    >
    > CMD="./sendcommand blah 127.0.0.1 2701 \"$*\""
    > eval $CMD

    As I said above, the single-quote syntax is fine...

    I copied the original script and changed "sendcommand" to "echo". I then ran
    the script. It works as expected except for the missing '$' on line 4 I already
    mentioned:

    #!/bin/sh

    CMD="echo blah 127.0.0.1 2701 '$*'"
    echo -n "CMD: $*"
    echo
    $CMD
    echo

    When I run it, I see:

    $ ./sendcmd a b c
    CMD: a b c
    blah 127.0.0.1 2701 'a b c'

    I can run it with shell debugging and I see:

    $ sh -vx ./sendcmd a b c
    #!/bin/sh

    CMD="echo blah 127.0.0.1 2701 '$*'"
    + CMD=echo blah 127.0.0.1 2701 'a b c'
    echo -n "CMD: $*"
    + echo -n 'CMD: a b c'
    CMD: a b cecho
    + echo

    $CMD
    + echo blah 127.0.0.1 2701 ''\''a' b 'c'\'''
    blah 127.0.0.1 2701 'a b c'
    echo
    + echo

    Sooo.. Not sure why it isn't behaving as expected. Give it a try yourself with
    'sh -vx' and see what you find out. Better yet, post it back.

    Kevin

  • Next message: Kevin Collins: "Re: Unix: List only File names and not directory"

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