Bash Programming – How to Create a Progress Bar to Visualize Wait Time

bashprogramming

In a bash script sometimes you need the user to wait some seconds for a background process to finish.

I usually use for example:

sleep 10

How can I add a kind of progressbar to the script, so the user knows how long to wait?

I installed the command bar but I don't understand the manual.

Best Answer

while true;do echo -n .;sleep 1;done &
sleep 10 # or do something else here
kill $!; trap 'kill $!' SIGTERM
echo done

this will start an infinite while loop that echos a spinner every second, executed in the background.

Instead of the sleep10 command run any command you want.

When that command finishes executing this will kill the last job running in the background (which is the infinite while loop)

source: https://stackoverflow.com/a/16348366/1069083

You can use various while loops instead, e.g. a spinner like this:

while :;do for s in / - \\ \|; do printf "\r$s";sleep 1;done;done

Related Solutions

Bash – Have Bash script wait for status message before continuing

You can use tail -f to keep reading from the file as it grows. Be careful with what you feed tail -f into. You can pipe tail -f into a filter that waits until the desired log line and quits. What won't work is if you pipe tail -f into a filter that pipes into another filter, because the intermediate filter will buffer its output. This works:

: >file.log  # create an empty log file
start-selenium-session --log-file=file.log &
{ tail -n +1 -f file.log & } | sed -n '/Started SocketListener/q'
speak-to-socket

Note that I put tail in the background. This is because when sed finds the desired line, it exits, but the pipeline keeps running as long as tail is waiting for the next line, which may not come immediately if at all¹. tail will exit when the next line comes and it receives a SIGPIPE. This may leave a stray tail process if the log is removed without any line being written to it (obtaining the PID of the tail process to kill it when sed exits would be possible but tricky).

¹ _{Thanks to Peter.O for pointing out the bug in an earlier version.}

Bash – Wait for background processes to finish with inverse match process ID

As others have said, there isn't any way to wait on "not" a process ID. However this pattern of code doesn't seem that bad to me, so I offer it as a suggested way of achieving what you're after.

It makes use of Bash arrays which you can then give as a list to the wait command.

Example

A modified version of your example code, cmd.bash.

!/bin/bash

array[0]=1
array[0]=2

sleep 30 &
pid=$!

pidArr=()
for i in ${array[@]}; do
  for n in $(seq 3); do
    if [ $n -eq 1 ]; then
      sleep 31 > file &
      pidArr+=($!)
    else
      sleep 32 >> file &
      pidArr+=($!)
    fi
  done
done

echo ${pidArr[@]}

I've substituted sleep commands in this example just to simulate some long running jobs that we can background. They have nothing to do with this other than to act as stand-ins.

Also the final echo command is there purely so we can see what happens when the for loops complete. Ultimately we'll replace it with an actual wait command, but let's not get ahead of ourselves.

Example run #1

So let's run our program and see what happens.

$ ./cmd.bash 
24666 24667 24668

Now if we check ps:

$ ps -eaf|grep sleep
saml     24664     1  0 22:28 pts/9    00:00:00 sleep 30
saml     24666     1  0 22:28 pts/9    00:00:00 sleep 31
saml     24667     1  0 22:28 pts/9    00:00:00 sleep 32
saml     24668     1  0 22:28 pts/9    00:00:00 sleep 32

If we wait a bit, these will ultimately finish. But this shows that if we add the process IDs to an array we can echo them out afterwards.

Example #2

So let's change that echo line out and swap in a wait line now, something like this:

  wait ${pidArr[@]}

Now when we run our modified version we see that it's waiting on ALL the process IDs:

$ ./cmd.bash

...after ~30 seconds passes

We get back our prompt. So we successfully waited for all the processes. A quick check of ps:

$ ps -eaf|grep sleep
$

So it worked.