Question

I have a bash script set that executes in a folder containing a number of photos and sequentially stitches them into panoramas based on the user input. Once the generation is completed, the output file is renamed to $x-pano.jpg and moved one folder higher.

My issue is the number prefix is based on the sequential execution of the script, meaning all files get renamed 1-pano.jpg to n-pano.jpg based on the number of panoramas generated during the script execution.

How can I modify the renaming process to look at the storage folder and get the largest $x? I want to increment that number by 1 and use as the file’s numerical prefix. My current code is

//get the list of files in directory and sort in increasing order
$filelist=$(find ../ -maxdepth 1 -type f | sort -n)

//get number of files
$length=${filelist[@]}

//get the last file
$lastFile=${fileList[$((length-1))]}

will get a list of the files, sort in increasing order and get the last file from the list. This is where I get stuck. Using - as a delimiter, how can I capture the current value?

Answer 1

You’re probably looking for the ${var%%foo} construct, which strips the longest foo from the end of a variable:

$ F=1-pano.jpg
$ echo ${F%%-pano.jpg}
1
$ F=1222-pano.jpg
$ echo ${F%%-pano.jpg}
1222

Try lastNum=${lastFile%%-pano.jpg}.