How to rename a zero-padded file sequence efficiently in ZSH? - find

Question

I have a picture sequence named with zero-padded numbers like so:
/path/to/file_07469.jpx
/path/to/file_07470.jpx
/path/to/file_07471.jpx
/path/to/file_07472.jpx
/path/to/file_07473.jpx
/path/to/file_07474.jpx
/path/to/file_07475.jpx
/path/to/file_07476.jpx
/path/to/file_07477.jpx
/path/to/file_07478.jpx
/path/to/file_07479.jpx
/path/to/file_07480.jpx
/path/to/file_07481.jpx
/path/to/file_07482.jpx
This is just an extract. It is thousands of files. I’d like to rename all files from a certain number on, adding / subtracting X. I’d love to use find with a regex.
#!/bin/zsh
shift=-1000
seqnumstart="$(echo "$1" | grep -Eo "\d+")"
bn="$(basename $1)"
bbn="$(echo "${bn%_*}")"
ext="$(echo "${bn##*.}")"
find "$(dirname $1)" -name "$bbn*$ext" -print0 | while read -d $'\0' file
do
seqnum="$(echo "$file" | grep -Eo "\d+")"
seqnum="$(echo "${seqnum#"${seqnum%%[!0]*}"}")"
if [[ "$seqnum" -ge "$seqnumstart" ]]; then
seqnumnew=$(($seqnum + $shift))
seqnumnew=$(printf %05d $seqnumnew)
filenew="$(echo $file | sed -E 's [0-9]+ '$seqnumnew' g')"
mv "$file" "$filenew"
fi
done
How can I improve my code? It is very slow. Im on a Mac (zsh).

Answer 1

zmv is a utility in zsh that can do a lot of filename manipulation and looping for you. Try this:
zmv -n 'p/file_(<7000-7999>).jpx' 'p/file_$(printf "%05d" $(($1 - 1000))).jpx'
Some of the pieces:
zmv: an autoload function; use autoload -Uz zmv to make it available (this is usually added to .zshrc).
-n: no-op. With this option, zmv will just print what would have happened, giving you an idea if the command is correct. Remove this to actually mv the files.
(...): grouping operator for zmv. This identifies sections in the name that you want to change; this section is referenced in the 'to' argument as $1.
<7000-7999>: glob operator for a range. Note that leading zeroes are not always required.
$(printf "%05d" ...): zero-padding.
$((...)): arithmetic.
$1: reference to the parenthetical value in the 'from' argument'. This is where zmv's magic happens - this is substituted for each matching filename.
As you likely know, you'll need to do the renaming in groups or in a specific order to avoid trying to change a name to a name that already exists. zmv will usually halt when it encounters collisions like that.

Answer 2

This is much faster:
#!/bin/zsh
shift=1000
seqnumstart="$(echo "$1" | grep -Eo "\d+")"
lastfile="$(find "$(dirname $1)" -name "*.jpx" | sort | tail -1)"
seqnumend="$(echo "$lastfile" | grep -Eo "\d+")"
bn="$(basename $1)"
bbn="$(echo "${bn%_*}")"
#extension
ext="$(echo "${bn##*.}")"
#basepath before the padded number
bp="$(echo "${1%_*}")"
function buildpath {
echo "$bp"_"$1"."$ext"
}
for i in {$seqnumstart..$seqnumend}
do
unpad="$(echo $i | sed 's/^0*//')"
seqnumnew="$(($unpad + $shift))"
seqnumnewpad="$(printf %05d $seqnumnew)"
op="$(buildpath "$i")"
np="$(buildpath "$seqnumnewpad")"
mv "$op" "$np"
done