find & remove characters in filenames


 
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# 8  
Awesome. I knew what IFS was, but I had never changed it before, and the whole leading/trailing spaces being stripped thing didn't occur to me before you mentioned it. Thanks for taking the time to explain that in such detail!

But wait.. So I understand the WHY now, but not specifically the HOW, i.e., how you used it in your original script.
Code:
while IFS= read -r

I don't get it... what is this actually setting IFS to? How are you setting a variable and then running a command without a semicolon or command substitution? Hmmm. I'm too tired to try to work this out right now.
# 9  
This type of variable assignment affects only the command it precedes (if you insert a semicolon between the assignment and the command the meaning changes):

with semicolon (IFS is affected inside the loop, a and b parsed correctly):

Code:
bash-4.1$ printf '%s:%s\n' a b | 
>   while IFS=:; read a b; do 
> printf 'IFS => '
> printf '%s' "$IFS" |
>   od -bc 
> printf '%s => %s\n'  a "$a"  b "$b"  
>   done
IFS => 0000000 072
          :
0000001
a => a
b => b

without semicolon (inside the loop IFS remains unchanged but a and b are still parsed correctly):

Code:
bash-4.1$ printf '%s:%s\n' a b | 
>   while IFS=: read a b; do 
> printf 'IFS => '
> printf '%s' "$IFS" |
>   od -bc 
> printf '%s => %s\n'  a "$a"  b "$b"  
>   done
IFS => 0000000 040 011 012
             \t  \n
0000003
a => a
b => b

From man bash (SIMPLE COMMAND EXPANSION):
Code:
       When a simple command is executed, the shell performs the following expansions, assignments, and redirections,
       from left to right.

       1.     The  words  that  the  parser has marked as variable assignments (those preceding the command name) and
              redirections are saved for later processing.

       2.     The words that are not variable assignments or redirections are expanded.  If any  words  remain  after
              expansion,  the first word is taken to be the name of the command and the remaining words are the argu-
              ments.

       3.     Redirections are performed as described above under REDIRECTION.

       4.     The text after the = in each variable assignment undergoes tilde expansion, parameter  expansion,  com-
              mand substitution, arithmetic expansion, and quote removal before being assigned to the variable.

       If  no  command  name  results, the variable assignments affect the current shell environment.  Otherwise, the
       variables are added to the environment of the executed command and do not affect the  current  shell  environ-
       ment.   If  any of the assignments attempts to assign a value to a readonly variable, an error occurs, and the
       command exits with a non-zero status.

Another example for this type of assignment:

Code:
bash-4.1$ a=1; a=2 awk 'BEGIN { printf "%s => %s\n", ARGV[0], ENVIRON["a"] }'; printf '%s => %s\n' "$0" "$a"
awk => 2
bash => 1

This User Gave Thanks to radoulov For This Post:
# 10  
wow, this is getting very technical for a mere noob like me!

One other quick question; I have a few mp3 files with a dot half way through the file name (ie track1 feat. artistx.mp3), up until now I have manually removed them as I came across it, how do I modify this command to remove them on mass?

Thanks!

Last edited by barrydocks; 12-20-2011 at 07:49 AM.. Reason: typo
# 11  
Code:
find . -type f -name '*.*.mp3' -exec rm {} +

Attention: the command above will remove all the files that have two (2) dots in their names and end by .mp3!

Make sure you have a valid backup before executing that command!
Try it without rm first:

Code:
find . -type f -name '*.*.mp3'

This User Gave Thanks to radoulov For This Post:
# 12  
sorry radoulov, you miss understood me: I want to remove the additional dot from the filename not delete the file?
Thanks
# 13  
OK, sorry!
Try this:

Code:
find . -type f -name '*.mp3' |
  while IFS= read -r; do
    p=${REPLY%/*} n=${REPLY#$p/}
    n=${n//[:?.\"]} n=${n%mp3}.mp3
    [ -f "$p/$n" ] && {
      printf >&2 '%s already exists\n' "$p/$n"
      continue  
        } ||
      mv -- "$REPLY" "$p/$n" 
  done

The code above will not overwrite existing files.
# 14  
Quote:
Originally Posted by radoulov
If no command name results, the variable assignments affect the current shell environment. Otherwise, the variables are added to the environment of the executed command and do not affect the current shell environment. If any of the assignments attempts to assign a value to a readonly variable, an error occurs, and the command exits with a non-zero status.
HOLY CRAP! 3.5 years since I started learning nix (and bash)--how the heck have I not seen this before! Wow. Thanks for the taking the time radoulov.

@barrydocks: Why do you want to remove dots from filenames? Since when do dots cause trouble on any os? I'm just curious...
 

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