# Exec with string in variables?

**URL:** <https://www.ruby-forum.com/t/exec-with-string-in-variables/92259>\
**Category:** Ruby\
**Created:** [April 17, 2007, 4:55pm UTC](https://www.ruby-forum.com/t/exec-with-string-in-variables/92259 "2007-04-17T16:55:36Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![caefer](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/e36b37/32.png) [@caefer](https://www.ruby-forum.com/u/caefer)\
**Post date:** [April 17, 2007, 4:55pm UTC](https://www.ruby-forum.com/t/exec-with-string-in-variables/92259/1 "2007-04-17T16:55:36Z")

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Hi,

i have something like this and more in perl and would transform it to  
ruby.  
First i changed system to exec and than the points to plus , but the  
strings which are in the scalar’s seems  
not be applied in the exec call , perhaps some special needs with  
quoting!?

:perl  
foreach $line(@methoden) {  
system("$exe\_path" . “dti.exe -qb -t -e$line $dom\_file  
$train\_file $modell\_string” . “$line” . “.dti”);  
…  
}

:ruby

methoden.each do |line|  
exec(“exe\_path + dti.exe -qb -t -eline dom\_file train\_file  
modell\_string + line + .dti”)  
…  
end

many thanks christian

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<div class="post-metadata">

**Author:** ![caefer](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/e36b37/32.png) [@caefer](https://www.ruby-forum.com/u/caefer)\
**Post date:** [April 17, 2007, 5:08pm UTC](https://www.ruby-forum.com/t/exec-with-string-in-variables/92259/2 "2007-04-17T17:08:39Z")

</div>

Try

exec("#{exe\_path dti.exe -qb -t -eline #{dom\_file} #{train\_file}  
#{modell\_string} #{line} .dti")

Ruby needs #{variable} in quotes to parse variable. Or you could  
concatenate outside the quotes like:

exec(exe\_path + “dti.exe -qb…” + dom\_file)

Basically, it is variable + “string” + another\_variable  
On Tue, 2007-04-17 at 23:55 +0900, Christian wrote:

> :perl  
> modell\_string + line + .dti")  
> …  
> end
> 
> many thanks christian

–

Thanks,

Ken M.  
Wireless Operations Engineer  
Farmers Wireless

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<div class="post-metadata">

**Author:** ![caefer](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/e36b37/32.png) [@caefer](https://www.ruby-forum.com/u/caefer)\
**Post date:** [April 17, 2007, 5:21pm UTC](https://www.ruby-forum.com/t/exec-with-string-in-variables/92259/3 "2007-04-17T17:21:41Z")

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On Apr 17, 10:53 am, Christian [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

> ```
> foreach $line(@methoden) {
> 
> ```
> 
> …  
> end
> 
> many thanks christian

String interpolation does this nicely:

methoden.each do |line|  
exec(“#{exe\_path}dti.exe -qb -t -e#{line} #{dom\_file} #{train\_file}  
#{modell\_string}#{line}.dti”)  
…  
end

---

<div class="post-metadata">

**Author:** ![caefer](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/e36b37/32.png) [@caefer](https://www.ruby-forum.com/u/caefer)\
**Post date:** [April 18, 2007, 7:33am UTC](https://www.ruby-forum.com/t/exec-with-string-in-variables/92259/4 "2007-04-18T07:33:03Z")

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On Tue, Apr 17, 2007 at 11:55:06PM +0900, Christian wrote:

> :perl  
> foreach $line(@methoden) {  
> system("$exe\_path" . “dti.exe -qb -t -e$line $dom\_file  
> $train\_file $modell\_string” . “$line” . “.dti”);  
> …  
> }

Instead of $var write #{var}

Alternatively, let Ruby deal with the individual arguments:

system(exe\_path, “-qb”, “-t”, “-e” + line, dom\_file, train\_file,  
modell\_string + line + “.dti”)

This is safer as it will work even if the arguments themselves contain  
spaces.