looping files with bash - bash

Question

I'm not very good in shell scripting and would like to ask you some question about looping of files big dataset: in my example I have alot of files with the common .pdb extension in the work dir. I need to loop all of them and i) to print name (w.o pdb extension) of each looped file and make some operation after this. E.g I need to make new dir for EACH file outside of the workdir with the name of each file and copy this file to that dir. Below you can see example of my code which are not worked- it's didn't show me the name of the file and didn't create folder for each of them. Please correct it and show me where I was wrong
#!/bin/bash
# set the work dir
receptors=./Receptors
for pdb in $receptors
do
filename=$(basename "$pdb")
echo "Processing of $filename file"
cd ..
mkdir ./docking_$filename
done
Many thanks for help,
Gleb

Answer 1

If all your files are contained within the .Repectors folder, you can loop each of them like so:
#!/bin/bash
for pdb in ./Receptors/*.pdb ; do
filename=$(basename "$pdb")
filenamenoextention=${filename/.pdb/}
mkdir "../docking_${filenamenoextention}"
done
Btw:
filenamenoextention=${filename/.pdb/}
Does a search replace in the variable $pdb. The syntax is ${myvariable/FOO/BAR}, and replaces all "FOO" substrings in $myvariable with "BAR". In your case it replaces ".pdb" with nothing, effectively removing it.
Alternatively, and safer (in case $filename contains multiple ".pdb"-substrings) is to remove the last four characters, like so: filenamenoextention=${filename:0:-4}
The syntax here is ${myvariable:s:e} where s and e correspond to numbers for the start and end index (not inclusive). It also let's you use negative numbers, which are offsets from the end. In other words: ${filename:0:-4} says: extract the substring from $filename starting from index 0, until you reach fourth-to-the-last character.
A few problems you have had with your script:
for pdb in ./Receptors loops only "./Receptors", and not each of the files within the folder.
When you change to parent directory (cd ..), you do so for the current shell session. This means that you keep going to the parent directory each time. Instead, you can specify the parent directory in the mkdir call. E.g mkdir ../thedir

Answer 2

You're looping over a one-item list, I think what you wanted to get is the list of the content of ./Receptors:
...
for pdb in $receptors/*
...

Answer 3

to list only file with .pdb extension use $receptors/*.pdb
So instead of just giving the path in for loop, give this:
for pdb in $receptors/*.pdb
To remove the extension :
set the variable ext to the extension you want to remove and using shell expansion operator "%" remove the extension from your filename eg:
ext=.pdb
filename=${filename%${ext}}
You can create the new directory without changing your current directory:
So to create a directory outside your current directory use the following command
mkdir ../docking_$filename
And to copy the file in the new directory use cp command
After correction
Your script should look like:
receptors=./Receptors
ext=.pdb
for pdb in $receptors/*.pdb
do
filename=$(basename "$pdb")
filename=${filename%${ext}}
echo "Processing of $filename file"
mkdir ../docking_$filename
cp $pdb ../docking_$filename
done