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Old 01-12-2009, 11:03 AM   #16
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Originally Posted by waqasdaar View Post
I am using "ffmpeg" which is a command line tool to convert multimedia files between formats. In a script ( i am using the ffmpeg comand like this

Sorry guys if I didnot mention the problem clearly.
No, we all understand the question. You are not reading the answers that are given. Your problem has been well-solved by the above posters, but you (still) haven't said what commands you're running that don't work, the sample script you've supposedly written, or given any feedback on the information you were directed to.
  1. Read the man page for the tail command. Look at the different options, and see which one fits your need. There is one.
  2. STDOUT and STDERR were referenced...research how to use them in a script. Lots of information out there

Do these things mentioned above, before posting back about how it doesn't work, and asking the same question again.
Old 01-12-2009, 01:14 PM   #17
Sergei Steshenko
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Originally Posted by waqasdaar View Post
The bold line continusely changing its value after converting the whole media file it prints at the end

video:120686kB audio:0kB global headers:0kB muxing overhead 0.000000%

I just trying to achieve that it only prints the Bold line. after it finish script return me the control back. Hope now you understand the problem.

Sorry guys if I didnot mention the problem clearly.

Thanks in Advanced.
OK, so here is a number of questions for you:

  1. Is the bold line in the you see in the terminal the same from the point of view of characters it contains as a line in a text file ?
  2. Is the bold line you see printed to stdout or stderr ?

Try to understand/answer these two questions first - in whatever order.

Maybe start from the simpler one - about stderr vs stdout - do you know how to find this out ?

Do you understand why these questions are asked ?
Old 01-12-2009, 02:44 PM   #18
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As previously mentioned by PTrenholme and indicated by others, you need to understand output redirection.

In a shell, type man bash and read the section on REDIRECTION.

The output you are getting is from stderr instead of stdout

When you redirect output using the > without a file descriptor, bash assumes that you mean stdout (File descriptor 1).

ffmpeg -i $1 -b 4000k -minrate 4000k -maxrate 4000k -bufsize 1835k temp.m2v > temp
is the same as:
ffmpeg -i $1 -b 4000k -minrate 4000k -maxrate 4000k -bufsize 1835k temp.m2v 1> temp
What you could do is redirect stderr (File descriptor 2):
ffmpeg -i $1 -b 4000k -minrate 4000k -maxrate 4000k -bufsize 1835k temp.m2v 1> temp 2> errors
I suspect (as does everyone else who has posted a response) that the line you are after is the last line of the new errors file.

If you look at my previous post you would see something like:
What this is saying is, redirect stderr to stdout (which is being redirected to the file temp.

What we have been saying, is that it is in your best interest to understand this as opposed to copy typing.

Last edited by Disillusionist; 01-12-2009 at 02:46 PM.


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