Recursive Shell Script and file extensions issue - bash

Question

I have a problem with this script. The script is supposed to go trough all the files and all sub-directories and sub-files (recursively). If the file ends with the extension .txt i need to replace a char/word in the text with a new char/word and then copy it into a existing directory. The first argument is the directory i need to start the search, the second is the old char/word, third the new char/word and fourth the directory to copy the files to. The script goes trough the files but only does the replacement and copies the files from the original directory. Here is the script
#!/bin/bash
funk(){
for file in `ls $1`
do
if [ -f $file ]
then
ext=${file##*.}
if [ "$ext" = "txt" ]
then
sed -i "s/$2/$3/g" $file
cp $file $4
fi
elif [ -d $file ]
then
funk $file $2 $3 $4
fi
done
}
if [ $# -lt 4 ]
then
echo "Need more arg"
exit 2;
fi
cw=$1
a=$2
b=$3
od=$4
funk $cw $a $b $od

Answer 1

You're using a lot of bad practices here: lack of quotings, you're parsing the output of ls... all this will break as soon as a filename contains a space of other funny symbol.
You don't need recursion if you either use bash's globstar optional behavior, or find.
Here's a possibility with the former, that will hopefully show you better practices:
#!/bin/bash
shopt -s globstar
shopt -s nullglob
funk() {
local search=${2//\//\\/}
local replace=${3//\//\\/}
for f in "$1"/**.txt; do
sed -i "s/$search/$replace/g" -- "$f"
cp -nvt "$4" -- "$f"
done
}
if (($#!=4)); then
echo >&2 "Need 4 arguments"
exit 1
fi
funk "$#"
The same function funk using find:
#!/bin/bash
funk() {
local search=${2//\//\\/}
local replace=${3//\//\\/}
find "$1" -name '*.txt' -type f -exec sed -i "s/$search/$replace/g" -- {} \; -exec cp -nvt "$4" -- {} \;
}
if (($#!=4)); then
echo >&2 "Need 4 arguments"
exit 1
fi
funk "$#"
In cp I'm using
the -n switch: no clobber, so as to not overwrite an existing file. Use it if your version of mv supports it, unless you actually want to overwrite files.
the -v switch: verbose, will show you the moved files (optional).
the -t switch: -t followed by a directory tells to copy into this directory. It's a very good thing to use cp this way: imagine instead of giving an existing directory, you give an existing file: without this feature, this file will get overwritten several times (well, this will be the case if you omit the -n option)! with this feature the existing file will remain safe.
Also notice the use of --. If your cp and sed supports it (it's the case for GNU sed and cp), use it always! it means end of options now. If you don't use it and if a filename start with a hyphen, it would confuse the command trying to interpret an option. With this --, we're safe to put a filename that may start with a hyphen.
Notice that in the search and replace patterns I replaced all slashes / by their escaped form \/ so as not to clash with the separator in sed if a slash happens to appear in search or replace.
Enjoy!

Answer 2

As pointed out, looping over find output is not a good idea. It also doesn't support slashes in search&replace.
Check gniourf_gniourf's answer.
How about using find for that?
#!/bin/bash
funk () {
local dir=$1; shift
local search=$1; shift
local replace=$1; shift
local dest=$1; shift
mkdir -p "$dest"
for file in `find $dir -name *.txt`; do
sed -i "s/$search/$replace/g" "$file"
cp "$file" "$dest"
done
}
if [[ $# -lt 4 ]] ; then
echo "Need 4 arguments"
exit 2;
fi
funk "$#"
Though you might have files with the same names in the subdirectories, then those will be overwritten. Is that an issue in your case?