CODEWITHSUNDEEP
linuxbashshell
Irbis
Irbis

Reputation: 61

Bash get last line (combined) from stdout

I have a script that performs many different operations and displays the status of their completion in a clear way for the user. I need a function so that some strings can be retrieved as variables for further processing. This is a highly simplified example:

#!/bin/bash

echo "Test script."
echo -n "1) cat file "
cat ./testfile.f &> /dev/null
if [ $? -eq 0 ]
then
    echo "$(tput hpa $(tput cols))$(tput cub 8)[OK]"
else
    echo "$(tput hpa $(tput cols))$(tput cub 8)[FAIL]"
fi
echo -n "2) make subfolder "
mkdir ./testdir &> /dev/null
if [ $? -eq 0 ]
then
    echo "$(tput hpa $(tput cols))$(tput cub 8)[OK]"
else
    echo "$(tput hpa $(tput cols))$(tput cub 8)[FAIL]"
fi

It take some as:

$./test.sh
Test script.
1) cat file                               [FAIL]
2) make subfolder                         [OK]

How can I get the last line (ideally, any string) during script execution? Ideally it would be using a function (so I could work with the resulting string) This string will be processed in the same script. So far, I see only one solution: redirect the output of each echo command using tee.

Is there any way to read the already outputted data!?

Upvotes: 2

Views: 802

Answers (1)

Walter A
Walter A

Reputation: 20032

Suppose that you have strings {1..5} that you need to process:

process() {
   while read -r input; do
      sleep 2
      echo "Processed ${input}."
   done
}

printf "line %s\n" {1..5} | process

In this situation you might want to see the numbers before they are being processed.
You can do this by duplicating stdout to fd 3 and use a function.

display() {
   while read -r input; do
      echo "=== ${input} ===" >&3
      echo "${input}"
   done
}

process() {
   while read -r input; do
      sleep 2
      echo "Processed ${input}."
   done
}

exec 3>&1
printf "line %s\n" {1..5} | display | process

Upvotes: 1

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