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• How does CMP pass comparison value to the next line in a bash script ?

  22 août 2015, par Tandy Freeman

  I want to compare the output of two framemd5 (decoded md5 of every video frame) digests.
  http://stackoverflow.com/a/12736416/2188572

  The cmp script works perfectly for me.
  I know next to nothing about coding, so I want to educate myself on what’s happening, and I can’t figure out from SO or googling.

  It seems like the script should require more input from me, like I should have to stipulate(apologies for awful pseudo code)

  cmp file1 file 2
  
  if cmp produces a difference;then
  
  else 

  It seems that just entering "if cmp file1 file 2" automatically produced the equivalent of a YES or NO and stores that info for the then, else etc ?

• Script - split video file in equivalent segments

  4 octobre 2014, par Code_Ed_Student

  I am currently using ffmpeg to slice video files. I automated the process through a script called ffmpeg_split.sh. To view the full script click HERE.
  When I ran this script on a few .mp4 files I had, it would return nothing :

  __DURATION_HMS=$(ffmpeg -i "$__FILE" 2>&1 | grep Duration | \
   grep '\d\d:\d\d:\d\d.\d\d' -o)

  NOTE : This is line #54.

  So without this value, the calls that come after it to the function parse_duration_info() are returning the error message.

  According to the comments in the original script, there should be 2 arguments to parse_duration_info().

  # arg1: duration in format 01:23:45.67
  
  # arg2: offset for group 1 gives hours, 2 gives minutes, 
  
  #       3 gives seconds, 4 gives milliseconds

  Here is the syntax to slice a video with script : ffmpeg_split.sh -s test_vid.mp4 -o video-part%03d.mp4 -c 00:00:08

  Belowe is where I parse the duration :

  function parse_duration_info() {
  
      if [[ $1 ]] && [[ $2 -gt 0 ]] && [[ $2 -lt 5 ]] ; then
  
          __OFFSET=$2
  
          __DURATION_PATTERN='\([0-9][0-9]\):\([0-9][0-9]\):\([0-9][0-9]\)\.\([0-9][0-9]\)'
  
          echo "$1" | sed "s/$__DURATION_PATTERN/\\$__OFFSET/"
  
      else
  
          echo "Bad input to parse_duration_info()"
  
          echo "Givven duration $1"
  
          echo "Givven offset $2"
  
          echo "Exiting..."
  
          exit 1
  
      fi
  
  }

• syntax error near unexpected token `do' in bash script

  11 mai 2016, par Avi

  I have bash script which takes 3 parameters from the command line. It compares all of the files in the directory to see if they are of the type of the first 2 parameters. If they are, the script converts such files to the type of the third parameter using an FFMPEG command. I would execute the script with the following command :

  ./convert.sh .avi .mp4 .flv 

  That this, this script would convert all of the .avi and .mp4 files to .flv.

  When I run the script, I get the error

  syntax error near unexpected token `do' in bash script.

  Here is the code :

  #!/bin/bash
  
  
  
  # $1 is the first parameter passed
  
  # $2 is the second parameter passed 
  
  # $3 is the third parameter passed
  
  
  
  for file in *.*; 
  
      do 
  
          #comparing the file types in the directory to the first 2 parameters passed
  
          if[  ( ${file: -4} == "$1" ) || ( ${file: -4 } == "$2" )  ]{
  
              export extension=${file: -4}
  
              #converting such files to the type of the first parameter using the FFMPEG comand
  
              do ffmpeg -i "$file" "${file%.extension}"$3;
  
  done