Using a variable in a system command

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May 7th, 2008, 09:24 AM

cowboyroy

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Using a variable in a system command

Is there a way to use a pre-defined variable in a system command.

my system command looks like this

system("/root/to/my/script `seq $variable`")

I thought i was being a bit too hopeful when i tried using the $variable
It works when i replace $variable with a number but the variable (the amount of times the script needs to run) depends on the users input.

Any ideas?

thanks

May 7th, 2008, 02:21 PM

keath

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Yes, a variable will work. What's with the backticks in your system command? Is that something your shell uses?

May 7th, 2008, 02:51 PM

Axweildr

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perl Code:

Original - perl Code
chomp $var; if (($var=~ /^\d+$/) && ($var>0)) { $cmd="/path/to/script seq $var"; @results=qx\|$cmd\|; for (@results) { print; } } else { print "invalid variable value\n"; }

chomp $var;
if (($var=~ /^\d+$/) && ($var>0)) {
  $cmd="/path/to/script seq $var";
  @results=qx|$cmd|;
  for (@results) { print; }
} else {
  print "invalid variable value\n";
}

always, always, always sanitize user input ... did I mention, always sanitize user input

Comments on this post

keath agrees: Yes. Absolutely critical. Bad idea to just accept user input and hand it to the shell.

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May 8th, 2008, 03:34 AM

cowboyroy

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cheers for the replies.
I am using back ticks because as far as I can tell thats the syntax when using the seq command e.g
./script `seq 2` will run it twice (with the parameters 1 and 2)
if i use
./script seq 2 it runs it with the parameters seq and 2
All of the user input will be fully validated before its used

and it turns out I was doing it correct, I just used the name of the input field rather than the variable that i made in my cgi script !!! (now i feel silly)

Cheers for your help and i hope i taught you something about seq

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