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Ubuntu – Asking for user input in a while loop in a bash script

I am running on Ubuntu 24.04.
I created a bash script that reads a file line by line in a loop and asks in this loop for a user input. (In fact it calls a function where this happens and something more, but to simplify my problem, we can ignore that)
Here is a simpel version of my script:

#!/bin/bash

REMOTE_CONFIG_LIST="./files_to_copy.txt"

while IFS=' ' read -r remote_file local_dest
do
        echo
        echo "Line = " "$remote_file" "$local_dest"
        read -p "Please enter your name: " name
        echo "Hello, $name!"
        echo

done < "$REMOTE_CONFIG_LIST"

I understand that the reason for a failure of that script is the fact that the first read is not finished while I start the 2nd read. What are my options here ?

Thanks in advance and best regards

Daniel

Actual result:
Line = /home/azureconf/conf/ubuntu/05-sentinelconnector.conf /etc/rsyslog.d
Hello, /home/azureconf/conf/ubuntu/rsyslog.conf /etc!

Expected result:
Line = /home/azureconf/conf/ubuntu/05-sentinelconnector.conf /etc/rsyslog.d
Please enter your name: Daniel
Hello, Daniel

Line = /home/azureconf/conf/ubuntu/rsyslog.conf /etc
Please enter your name: Daniel
Hello, Daniel

Tags:

4

Answers


  1. 0

    You can direct your file read to use file descriptor 3, rather than the standard which then conflicts when you also ask for the user input. This will keep them separate.

    while read -r -u3
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  2. 0

    Use a dedicated file descriptor:

    Under bash, you could generate temporary unnamed fifo, then link them do a free file descriptor and store his value into a variable by simply: {varname}< syntax:

    #!/bin/bash

REMOTE_CONFIG_LIST="./files_to_copy.txt"

while IFS=' ' read -ru $CONFIG remote_file local_dest; do
    echo
    echo "Line = " "$remote_file" "$local_dest"
    read -p "Please enter your name: " name
    echo "Hello, $name!"
    echo
done  {CONFIG}< "$REMOTE_CONFIG_LIST"
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  3. 0

    Since you asked for options – if the file or dest are unique then you could always read the file into an associative array first then loop on its contents, e.g. untested

    #!/usr/bin/env bash

REMOTE_CONFIG_LIST="./files_to_copy.txt"

declare -A file2dest
while IFS=' ' read -r remote_file local_dest; do
        file2dest["$remote_file"]="$local_dest"
done < "$REMOTE_CONFIG_LIST"

for remote_file in "${!file2dest[@]}"; do
        local_dest="${file2dest[$remote_file]}"
        echo
        echo "Line = " "$remote_file" "$local_dest"
        read -p "Please enter your name: " name
        echo "Hello, $name!"
        echo
done

    Use whichever value is unique as the array index.

    If neither are unique then you could do the same with an indexed array:

    #!/usr/bin/env bash

REMOTE_CONFIG_LIST="./files_to_copy.txt"

declare -a file_dest
while IFS= read -r line; do
        file_dest+=( "$line" )
done < "$REMOTE_CONFIG_LIST"

for line in "${file_dest[@]}"; do
        remote_file="${line% *}"
        local_dest="${line#* }"
        echo
        echo "Line = " "$remote_file" "$local_dest"
        read -p "Please enter your name: " name
        echo "Hello, $name!"
        echo
done
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  4. 0

    Another approach would be to preload the file.
    That’s not a great idea if it’s very big, but if you are prompting the user on every line I assume it isn’t millions or even hundreds of lines, so this approach should be simple and workable.

    REMOTE_CONFIG_LIST="./files_to_copy.txt"
mapfile -t list < "$REMOTE_CONFIG_LIST" # load the whole file to an array
for line in "${list[@]}"               # loop over the array
do  remote_file="${line% *}"           # parse out the first field
    local_dest="${line#* }"            # parse out the second field
    echo "Line = $remote_file $local_dest"
    read -p "Please enter your name: " name
    printf "Hello, %s!nn" "$name"
done

    This smacks strongly of an X/Y Problem, though.
    You might get better answers if you explain what you are trying to accomplish.

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