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I need to write a shell script that traverses a given directory structure in multiple levels, recognizes the video files scattered in the folders and copies all of them to another single folder. The video files are really Macromedia Flash data files (saved in my browser's cache) and they do not have any particular extension like .MP4 or .FLV just aplhanumeric names.

Now, I managed to make a start:

#!/bin/bash

#This script checks if the given folder contains video file and copies them another folder

filePath=$1                 #the argument(The folder Path)

if [[ -z "$filePath" ]]; then  #empty argument check

    echo "Please input the folder to search"

    exit 1

fi

if [ -d "$filePath" ]; then 

 if [ -L "$filePath" ]; then #check if the input folder is a valid folder

  echo "directory $file does not exist"

  exit 1

 fi 

else  #improper input given by the user     

 echo "$filePath is either not a valid directory or it is a file.Please enter a valid directory address" 

 exit 1

fi

find $filePath type -d |  #the find here list all the files and directories in the given folder

while read i 

do

    if [[ -d "$i" ]]; then

        idDirectory    #Call the function

    elif [[ -f "$i" ]]; then

#check if its the file in the expected format

#do the copy work

    fi

done

exit 0





idDirectory(){ # A recursive function to go multiple levels of the directory tree

    #the function which tells if the path is directory or file

    #If its a directory then it will call itself, till it gets a file

    #need some help here!!!!!

}

I need to write the recursive function that identifies and traverses directories.I tried this.
but it was not successful.

Some general shell programming principles:

• Always put double quotes around variable substitutions (unless you know that you need the unquoted behavior). "$foo" means the value of the variable foo, but $foo outside quotes undergoes further processing.


• The same goes for command substitutions: "$(foo)".


• 
  while read i; do … strips off leading and trailing whitespace and backslashes. Use while IFS= read pr i; do … to process lines exactly.

find $filePath type -d only lists directories.

Piping find into while read isn't the easiest or most robust way of executing a shell command for each file. Use the -exec action in find to process files robustly without getting into trouble with file names containing special characters such as whitespace. If you need more than one command, invoke sh; to process a file at a time:

find … -exec sh -c 'command1 "$0"; command2 "$0"' {} ;

To speed things up a little, you can use a more complex idiom which groups files to reduce the number of successive shell invocations:

find … -exec sh -c 'for x; do command1 "$x"; command2 "$x"; done' _ {} +

All the checks at the beginning of your script are useless or mostly useless. You don't care if the argument is a symbolic link, for example, and your error message in that case is incorrect.

I assume that your script is called with two arguments, the source directory and the destination directory. You can use mkdir -p to create target directories as needed. It helps to run find on the current directory, to avoid having to do file name manipulation to compute target paths.

Call file to check the type of a file based on its content. You may want to tweak the file formats that are accepted.

cd "$1" || exit

find . -type f -exec sh -c '

  # $0 = target directory; $1 = source file

  case "$(file "$1");" in

    video/x-flv;*)

      mkdir -p "$0/${1%/*}"    # create target subdirectory if needed

      cp -p "$1" "$0/$1"       # copy the file under the same relative path

  esac

' "$2" {} ;

Here is a script with a recursive function, which does what you were looking for:

#!/bin/bash



if [ "$#" -ne 1 ]; then

   echo "usage: "$0" <search_dir>"

   exit 1

fi



# recursive function to walk a directory tree

walktree() {

  # $1 is the function parameter

  local files=$(find "$1" -maxdepth 1 -type f)          # find all files in the current dir



  for file in $files; do                                # iterate through all found files

    if [[ "$(file "$file")" == *video/x-flv* ]]; then   # check the file content

      echo "found one"

      # put your copy code here

    fi

  done



  local subdirs=$(find "$1" -maxdepth 1 -type d)        # find all sub-directories



  for dir in $subdirs; do                               # iterate through all sub-directories

    if [ "$dir" != "$1" ]; then                         # omit the current directory

      walktree "$dir"                                   # call the recursive function

    fi

  done

}



walktree "$1"                                           # first call with <search_dir>

However, I would still recommend you to just use find . -type f as explained by Gilles.