[SOLVED] Bash noob: Not able to make bash for loop interactive

devaj · 08-13-2012, 06:43 AM

Hi,
I have been trying to get around renaming a couple of files in the using the bash for loop.However I am not able to make any command passed to for loop interactive whether I am root or not.
Here is the code:

Code:

for i in $(ls);do mv -i "$i" "$i.not";done

Same for removing :

Code:

for i in $(ls);do rm -i $i;done

I do know there are other ways to achieve the same result,but I would just like to know why does the for loop act like this.

grail · 08-13-2012, 07:42 AM

Tested the rm option here and it worked fine. My only change is that using ls is a complete no no, so try:

Code:

for i in *; do rm -i "$i"; done

rosehosting.com · 08-13-2012, 07:49 AM

This should work

Code:

#!/bin/bash
for i in $(find /path/to/files/ -type f); do
    read -p "Move $i to ${i}.bak (y/n)" yes_no
    [ "$yes_no" == "y" ] && mv $i ${i}.bak
done

H_TeXMeX_H · 08-13-2012, 08:19 AM

See 'man rename', or provide example.

You can just do 'rm -i *'.

devaj · 08-13-2012, 08:52 AM

Thank you all for replying.
I do know there are various other ways to renaming or removing a file (eg:the above method by H_TEXMEX_H or via awk,sed).What I really would like to know is when I use mv -i in the terminal,it prompts me for my input,but if I use mv -i in a for loop,it doesn't prompt me,not even once.Could anyone please tell me why does bash do this,the reason behind bash's behaviour.

P.S:Thank you Grail for letting me know that I shouldn't be using ls for input.Shall keep that in mind.May I ask you why exactly should you not use ls for input.

grail · 08-13-2012, 10:08 AM

Firstly, the answer to your issue with mv. You need to read the man page a little closer (I had to too

). The '-i' option for mv is only interactive if the file you are moving
to already exists:

Code:

$ ls
f1  f2
$ for i in *; do mv -i $i $i.old; done
$ ls
f1.old  f2.old
$ touch f1 f2
$ ls
f1  f1.old  f2  f2.old
$ for i in *; do mv -i $i $i.old; done
mv: overwrite `f1.old'? n
mv: overwrite `f2.old'? n
$ ls
f1  f1.old.old  f2  f2.old.old

So the things to notice here are:

1. When the destination name does not exist there is no prompting
2. Due to step 1, the final results are probably not what was expected

Quote:

May I ask you why exactly should you not use ls for input.

Always happy to answer questions

See the following link for answers:

http://mywiki.wooledge.org/ParsingLs

devaj · 08-13-2012, 10:42 AM

Thank you grail.I got more than I asked for.You Sir, ROCK

Shall be marking this thread solved.
GOD bless all.