CODEWITHSUNDEEP
bashshellscriptingwebcamstdout
Marshall Moutenot
Marshall Moutenot

Reputation: 121

Reroute File Output to stdout in Bash Script

I have a script, wacaw (http://webcam-tools.sourceforge.net/) that outputs video from my webcam to a file. I am trying to basically stream that to some sort of display i.e vlc, quicktime, etc to get a "mirror" type effect.

Aside from altering the source code for wacaw, is there any way to force a script's file output to stdout so I can pipe it to something like vlc? Is it even possible to stream video like that?

Thanks for your help!

UPDATE: just to clarify:

running the wacaw script is formatted as follows:

./wacaw --video --duration 5 --VGA myFile

and it outputs a file myFile.avi. If I try to do a named pipe:

mkfifo pipe
./wacaw --video --duration 5 --VGA pipe

it outputs a file pipe.avi

Upvotes: 1

Views: 955

Answers (3)

gunder
gunder

Reputation: 21

You may also try using tail -F myFile.avi:

# save stdout to file stdout.avi
man tail | less -p '-F option'
(rm -f myFile.avi stdout.avi; touch myFile.avi; exec tail -F myFile.avi > stdout.avi ) &
rm -f myFile.avi; wacaw --video --duration 1 --VGA myFile

md5 -q myFile.avi stdout.avi
stat -f "bytes: %z" myFile.avi stdout.avi

# pipe stdout to mplayer (didn't work for me though)
# Terminal window 1
# [mov,mp4,m4a,3gp,3g2,mj2 @ ...]moov atom not found
#rm -f myFile.avi; touch myFile.avi; tail -F myFile.avi | mplayer -cache 8192 -   
# Terminal window 2
#rm -f myFile.avi; wacaw --video --duration 1 --VGA myFile

Upvotes: 2

thomasa88
thomasa88

Reputation: 723

At least in bash you can do like this:

Original command:

write-to-file-command -f my-file -c

Updated command:

write-to-file-command -f >(pipe-to-command) -c

write-to-file-command will think >(pipe-to-command) is a write-only file and pipe-command will receive the file data on its stdin.

(If you just want the output to stdout you could do

write-to-file-command >(cat)

)

Upvotes: 3

drysdam
drysdam

Reputation: 8637

You can use named pipes. You use mkfifo to create the pipe, hand that filename to the writing process and then read from that file with the other process. I have no idea if video in particular would work that way, but many other things do.

Upvotes: 3

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