How to do a specific action on the first iteration of a while loop in a bash script

Question

I need to make a script do a specific action on first loop iteration.

for file in /path/to/files/*; do
    echo "${file}"
done

I want this output:

First run: file1
file2
file3
file4
...

Answer 1

A very common arrangement is to change a variable inside the loop.

noise='First run: '
for file in /path/to/files/*; do
    echo "$noise$file"
    noise=''
done

Answer 2

You can create an array with the files, then remove and keep the first element from this array, process it separately and then process the remaining elements of the array:

# create array with files
files=(/path/to/files/*)

# get the 1st element of the array
first=${files[0]}

# remove the 1st element of from array
files=("${files[@]:1}")

# process the 1st element
echo First run: "$first"

# process the remaining elements
for file in "${files[@]}"; do
   echo "$file"
done