# Looping through files using exec

**URL:** <https://www.ruby-forum.com/t/looping-through-files-using-exec/62269>\
**Category:** Ruby\
**Created:** [January 18, 2006, 5:45am UTC](https://www.ruby-forum.com/t/looping-through-files-using-exec/62269 "2006-01-18T05:45:34Z")\
**Posts on this page:** 6\
**Page:** 1

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**Author:** ![inari](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/i/838e76/32.png) [@inari](https://www.ruby-forum.com/u/inari)\
**Post date:** [January 18, 2006, 5:45am UTC](https://www.ruby-forum.com/t/looping-through-files-using-exec/62269/1 "2006-01-18T05:45:34Z")

</div>

I’m trying to do a mass encode of a large directory of media files but  
I’m not having much luck. I tried to use bash but it doesn’t like  
filenames with spaces so now I’m trying to do it with ruby but using the  
exec command it executes the first line then finishes. Here’s what I’ve  
done in the IRB.

Dir["\*.avi"].each {|x| exec (“mencoder “” + x + “” -vf scale=320:240  
-ovc lavc -lavcopts vcodec=mpeg4:vbitrate=150 -oac mp3lame -lameopts  
vbr=3:br=64 -o “Done\” + x + “””) }

It would be sweetness on a stick if it worked but unfortunately it stops  
after the first one. Can anyone tell me what I’m doing wrong and more  
importantly what I need to do to make this work?

Thanks in advance,

I

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<div class="post-metadata">

**Author:** ![inari](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/i/838e76/32.png) [@inari](https://www.ruby-forum.com/u/inari)\
**Post date:** [January 18, 2006, 6:19am UTC](https://www.ruby-forum.com/t/looping-through-files-using-exec/62269/2 "2006-01-18T06:19:59Z")

</div>

You said bash…

Does “Done” represent a directory? and… does Done#{filename} work  
with this option? I would have thought that in \*nix, it would be  
Done/#{filename}

Not exactly sure what this app is supposed to do but the loop looks ok…

irb(main):004:0\> puts “mencoder “” + x + “” -vf scale=320:240 -ovc  
lavc -lavcopts vcodec=mpeg4:vbitrate=150 -oac mp3lame -lameopts  
vbr=3:br=64 -o “Done\” + x + “””  
mencoder “pron.avi” -vf scale=320:240 -ovc lavc -lavcopts  
vcodec=mpeg4:vbitrate=150 -oac mp3lame -lameopts vbr=3:br=64 -o  
“Done\pron.avi”

---

<div class="post-metadata">

**Author:** ![inari](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/i/838e76/32.png) [@inari](https://www.ruby-forum.com/u/inari)\
**Post date:** [January 18, 2006, 6:39am UTC](https://www.ruby-forum.com/t/looping-through-files-using-exec/62269/3 "2006-01-18T06:39:14Z")

</div>

vrtwo lastname wrote:

> You said bash…
> 
> Does “Done” represent a directory? and… does Done#{filename} work  
> with this option? I would have thought that in \*nix, it would be  
> Done/#{filename}
> 
> Not exactly sure what this app is supposed to do but the loop looks ok…
> 
> irb(main):004:0\> puts “mencoder “” + x + “” -vf scale=320:240 -ovc  
> lavc -lavcopts vcodec=mpeg4:vbitrate=150 -oac mp3lame -lameopts  
> vbr=3:br=64 -o “Done\” + x + “””  
> mencoder “pron.avi” -vf scale=320:240 -ovc lavc -lavcopts  
> vcodec=mpeg4:vbitrate=150 -oac mp3lame -lameopts vbr=3:br=64 -o  
> “Done\pron.avi”

If I replace exec with puts it lists the commands fine. My problem is  
that when I use exec it runs the first command fine then exits ignoring  
all the other files. For example if I have a directory that has the  
files:

bar1.avi  
bar2.avi  
bar3.avi

and I use the following in IRB:

Dir["\*.avi"].each {|x| puts (“mencoder “” + x + “” -vf scale=320:240  
-ovc lavc -lavcopts vcodec=mpeg4:vbitrate=150 -oac mp3lame -lameopts  
vbr=3:br=64 -o “Done\” + x + “””) }

I get the following output:

mencoder “\bar1.avi” -vf scale=320:240 -ovc lavc -lavcopts  
vcodec=mpeg4:vbitrate=150 -oac mp3lame -lameopts vbr=3:br=64 -o  
“Done\bar1.avi”  
mencoder “\bar2.avi” -vf scale=320:240 -ovc lavc -lavcopts  
vcodec=mpeg4:vbitrate=150 -oac mp3lame -lameopts vbr=3:br=64 -o  
“Done\bar2.avi”  
mencoder “\bar3.avi” -vf scale=320:240 -ovc lavc -lavcopts  
vcodec=mpeg4:vbitrate=150 -oac mp3lame -lameopts vbr=3:br=64 -o  
“Done\bar3.avi”

but if I do:

Dir["\*.avi"].each {|x| puts (“mencoder “” + x + “” -vf scale=320:240  
-ovc lavc -lavcopts vcodec=mpeg4:vbitrate=150 -oac mp3lame -lameopts  
vbr=3:br=64 -o “Done\” + x + “””) }

It will only execute:  
mencoder “\bar1.avi” -vf scale=320:240 -ovc lavc -lavcopts  
vcodec=mpeg4:vbitrate=150 -oac mp3lame -lameopts vbr=3:br=64 -o  
“Done\bar1.avi”

---

<div class="post-metadata">

**Author:** ![inari](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/i/838e76/32.png) [@inari](https://www.ruby-forum.com/u/inari)\
**Post date:** [January 18, 2006, 6:41am UTC](https://www.ruby-forum.com/t/looping-through-files-using-exec/62269/4 "2006-01-18T06:41:08Z")

</div>

Hi,

At Wed, 18 Jan 2006 13:09:23 +0900,  
Jason C. wrote in [ruby-talk:176073]:

> I’m trying to do a mass encode of a large directory of media files but  
> I’m not having much luck. I tried to use bash but it doesn’t like  
> filenames with spaces so now I’m trying to do it with ruby but using the  
> exec command it executes the first line then finishes. Here’s what I’ve  
> done in the IRB.

exec replaces current process with invoked command, use system  
instead.

> Dir["\*.avi"].each {|x| exec (“mencoder “” + x + “” -vf scale=320:240  
> -ovc lavc -lavcopts vcodec=mpeg4:vbitrate=150 -oac mp3lame -lameopts  
> vbr=3:br=64 -o “Done\” + x + “””) }

And also bash should work if you quote names properly:

opts="-vf scale=320:240 -ovc lavc -lavcopts vcodec=mpeg4:vbitrate=150  
-oac mp3lame -lameopts vbr=3:br=64"  
for x in \*.avi; do  
mencoder “$x” $opts -o “Done “$x””  
done

---

<div class="post-metadata">

**Author:** ![inari](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/i/838e76/32.png) [@inari](https://www.ruby-forum.com/u/inari)\
**Post date:** [January 18, 2006, 6:47am UTC](https://www.ruby-forum.com/t/looping-through-files-using-exec/62269/5 "2006-01-18T06:47:10Z")

</div>

Hi,

At Wed, 18 Jan 2006 14:03:36 +0900,  
nobuyoshi nakada wrote in [ruby-talk:176077]:

> > Dir["\*.avi"].each {|x| exec (“mencoder “” + x + “” -vf scale=320:240  
> > -ovc lavc -lavcopts vcodec=mpeg4:vbitrate=150 -oac mp3lame -lameopts  
> > vbr=3:br=64 -o “Done\” + x + “””) }

Sorry, misread the command.

> And also bash should work if you quote names properly:
> 
> opts="-vf scale=320:240 -ovc lavc -lavcopts vcodec=mpeg4:vbitrate=150 -oac mp3lame -lameopts vbr=3:br=64"  
> for x in \*.avi; do  
> mencoder “$x” $opts -o “Done/$x”

---

<div class="post-metadata">

**Author:** ![inari](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/i/838e76/32.png) [@inari](https://www.ruby-forum.com/u/inari)\
**Post date:** [January 18, 2006, 7:09am UTC](https://www.ruby-forum.com/t/looping-through-files-using-exec/62269/6 "2006-01-18T07:09:31Z")

</div>

nobuyoshi nakada wrote:

> Hi,
> 
> At Wed, 18 Jan 2006 13:09:23 +0900,  
> Jason C. wrote in [ruby-talk:176073]:
> 
> > I’m trying to do a mass encode of a large directory of media files but  
> > I’m not having much luck. I tried to use bash but it doesn’t like  
> > filenames with spaces so now I’m trying to do it with ruby but using the  
> > exec command it executes the first line then finishes. Here’s what I’ve  
> > done in the IRB.
> 
> exec replaces current process with invoked command, use system  
> instead.
> 
> > Dir["\*.avi"].each {|x| exec (“mencoder “” + x + “” -vf scale=320:240  
> > -ovc lavc -lavcopts vcodec=mpeg4:vbitrate=150 -oac mp3lame -lameopts  
> > vbr=3:br=64 -o “Done\” + x + “””) }
> 
> And also bash should work if you quote names properly:
> 
> opts="-vf scale=320:240 -ovc lavc -lavcopts vcodec=mpeg4:vbitrate=150  
> -oac mp3lame -lameopts vbr=3:br=64"  
> for x in \*.avi; do  
> mencoder “$x” $opts -o “Done “$x””  
> done

Sweetness! Thanks! Actually now it seems that all my created files are  
in the same directory prefaced by ‘\Done’ instead of going in the Done  
directory. Go figure. Oh well. At least I can encode en masse! Good  
thing too. I’ve got a 50+ files to re-encode (a series) for my  
pocketpc. When you can stuff 15 hours of video on a 1gb sd card that’s  
a good thing™.

My bash script was similar but I didn’t have the quotes.

Thanks again!

J