Bash Script: How to remove temp file when terminated from keyboard?

ddenial · 05-12-2020, 10:52 AM

Hello All

I have written a bash script that encodes all video files in a directory to h265 (hevc) codec to reduce storage file size. First, the script encodes the video file to a temp file, and then when encoding is successful, it renames that temp file to the original file and finally removes that temp file.

But if I press Ctrl+C in-between, I want to remove that temp file. I have specified trap command at the beginning of the script. The temp file is created later.

How do achieve that? Is it even possible?

For some reason, I'm unable to copy and paste the script, so I've attached full script for reference.

Also, this is my first big script. I've concentrated only on logic rather than performance. I really appreciate pointing to any flaws in it.

Thanks.

pan64 · 05-12-2020, 10:57 AM

you need to set a trap on EXIT

shruggy · 05-12-2020, 11:59 AM

Firstly, I'd use mktemp for this

Code:

outputFileName="$inputFileFldr/$(tr -c -d 0-9 < /dev/urandom | head -c 15).mp4"

Code:

outputFileName=$(mktemp -u -p "$inputFileFldr" XXXXXXXXXXXXXXX.mp4)

Secondly, as pan64 said, you should remove this file in the trap action on EXIT:

Code:

trap 'rm -f "$outputFileName" >/dev/null 2>&1' 0

Thirdly, you should trap INT, and maybe also HUP, QUIT, PIPE, TERM, and ensure exit on them that will lead to the file being deleted as well.

Code:

trap 'echo "Oops! hevc ($$) is terminated."; exit 3' 1 2 3 13 15

ddenial · 05-12-2020, 12:03 PM

Quote:

Originally Posted by pan64

you need to set a trap on EXIT

Do you mean at the end of the script?

Trap code:

Code:

trap ' echo "Oops! hevc ($$) is terminated." ; exit 3 ' INT

When put at the beginning of the script:

Code:

$ hevc -e
Converting: 1/1
    Input : 'Spencer.mkv'
    Output: './355932967073595.mp4'
    Info  : '11.7 MiB' 'AVC' '1920x1080' '00:00:12.041' '160090'
frame=   29 fps=7.6 q=-0.0 Lsize=     235kB time=00:00:01.31 bitrate=1460.6kbits/s speed=0.344x    
Oops! hevc (32461) is terminated.

But when put at the end of the script:

Code:

$ hevc -e
Converting: 1/1
    Input : 'Spencer.mkv'
    Output: './095847693918920.mp4'
    Info  : '11.7 MiB' 'AVC' '1920x1080' '00:00:12.041' '160090'
frame=   28 fps=7.4 q=-0.0 Lsize=     228kB time=00:00:01.25 bitrate=1488.8kbits/s speed=0.333x    
COMMAND failed

ddenial · 05-12-2020, 12:07 PM

Quote:

Originally Posted by shruggy

Firstly, I'd use mktemp for this

Code:

outputFileName="$inputFileFldr/$(tr -c -d 0-9 < /dev/urandom | head -c 15).mp4"

Code:

outputFileName=$(mktemp -u -p "$inputFileFldr" XXXXXXXXXXXXXXX.mp4)

Secondly, as pan64 said, you should remove this file in the trap action on EXIT:

Code:

trap 'rm -f "$outputFileName" >/dev/null 2>&1' 0

Thirdly, you should trap INT, and maybe also HUP, QUIT, PIPE, TERM, and ensure exit on them that will lead to the file being deleted as well.

Code:

trap 'echo "Oops! hevc ($$) is terminated."; exit 3' 1 2 3 13 15

Need some time to digest. I'll get back after understanding traps more. Thanks

pan64 · 05-12-2020, 12:18 PM

no, there is a special trap:

Code:

trap cleanup EXIT
function cleanup() {
   cleanup at exit
}

ArfaSmif · 05-12-2020, 10:03 PM

This is what I have in some of my scripts as per pan64 above:-

trap CleanUp 1 2 3 15 18

CleanUp()
{
rm -f $tempfile
exit 0
}

where "tempfile" is defined somewhere in your script.

ddenial · 05-13-2020, 10:10 AM

I ended up doing the following changes.

Code:

#!/bin/bash

CleanUpTrap() {
        echo "Oops! hevc ($$) is terminated."
        find "$PWD" -type f -name "hevctmp420_*.mp4" -delete 2>/dev/null
        exit 2
}
trap 'CleanUpTrap' SIGHUP SIGINT SIGQUIT SIGQUIT SIGTERM
.
.
.
outputFileName="$(mktemp -u -p "$inputFileFldr" hevctmp420_XXXXXXXXXXXXXXX.mp4)"
.
.
.

I didn't specify the EXIT signal because the regular and clean exit of the script itself takes care of the temp file. The problem was only when it was interrupted forcefully.

pan64 · 05-13-2020, 10:19 AM

the exit trap executed always, regardless of any error/signal/whatever. But you know what you need.