(BASH) 将循环变量传递给将存储在变量中的命令

Question

I am trying to iterate through a line-by-line list of file ID strings (testIDs.txt) and pass them to an AWS command. The command should utilize the loop variable, and the output of the command should be stored in the "folder" variable. Whenever I run the script, I get blank spaces as output in the terminal.

#!bin/bash

while read p; do
    folder=$(aws s3 ls s3://a-bucket/ --recursive | grep "${p}" | cut -c 32-)
    echo "${folder}"
done < testIDs.txt    

The output of the AWS command should be two strings, and I have checked that this is true by running the AWS line separately in the terminal and using a string instead of ${p} .

Note: Right now, I simply want to print folder , but later I will pass folder to another loop.

Answer 1

You may want to just use two for loops, (1) read contents of the bucket to temp (optional/could search it directly), (2) Loop through IDs and (3) loop through each line of the bucket and look for the ID.

Example:

Read the folder structure to local temp, then for every ID look at the line of the file check for the testIDs and print them to a results file.

#!bin/bash
TMP="/tmp/s3-log-${RANDOM}.dat"
RESULTS="/tmp/s3-log-results.txt"
ID_FILE="testIDs.txt"

> "${RESULTS}"
aws s3 ls s3://a-bucket/ --recursive > "${TMP}"
while read p; do
    while IFS= read -r line ;do
        if ! [[ $line = *"${p}"* ]]; then
            echo "id: ${p} => $(echo ${line} | cut -c 32-)"  | tee -a "${RESULTS}"
        fi
    done < "${TMP}"        
done < "${ID_FILE}"

Answer 2

This is probably what you're looking for; use the while loop if you don't know how many values you need to loop through:

while read -r -d $'\t' resourceName; do
    echo "$resourceName"
done <<< "$(aws transfer list-servers --query='Servers[*].ServerId' --output text)"

In this case it's the -d $'\t' that influences the Bash word-splitting on the list of output AWS resources.