Editing a shell file while running it affects its behavior?

KansaiRobot

2/16/24, 10:59 AM

I am using the bash shell. Today talking with a colleague, he told me something that I found surprising and I would like to confirm it.

Say I have a shell script like this

#!/bin/bash

set -eu

python some_really_long_script.py

So I start executing it by running ./the_shell_script.sh.

Now, the command takes time. Probably hours.

My question is, if I edit this script file like this

#!/bin/bash

set -eu

python some_really_long_script.py

python some_other_really_long_script.py

and I save it, will the next command be executed after the first one?

I thought that the script was read to memory and executed so editing would have no impact but I was told this is possible.

EDIT1 I am calling my sh from a container with these details

cat /etc/os-release 
NAME="Ubuntu"
VERSION="20.04.4 LTS (Focal Fossa)"
ID=ubuntu
ID_LIKE=debian
PRETTY_NAME="Ubuntu 20.04.4 LTS"
VERSION_ID="20.04"
HOME_URL="https://www.ubuntu.com/"
SUPPORT_URL="https://help.ubuntu.com/"
BUG_REPORT_URL="https://bugs.launchpad.net/ubuntu/"
PRIVACY_POLICY_URL="https://www.ubuntu.com/legal/terms-and-policies/privacy-policy"
VERSION_CODENAME=focal
UBUNTU_CODENAME=focal

I checked and outside the container the release is different

0 + 5

command-line

bash

scripts

guiverc

2/16/24, 11:08 AM

You haven't provided any OS/product/release details; but in my own usage I've found the running scripts do not notice later edits (*during execution*) as the scripts are usually small & thus cached in buffers used by the running shell, thus no need to re-read from files (where inodes for file contents may have changed anyway)

KansaiRobot

2/16/24, 11:42 AM

since this is an ubuntu forum, I assumed linux is assumed. I also have always assumed the script is read in memory so not reread after edit, but my colleague said it is possible Therefore my question

guiverc

2/16/24, 12:02 PM

https://ubuntuforums.org/ is the site of Ubuntu Forums, this is a Ubuntu Q&A site; and I do consider the OS/release, even Ubuntu product matters. I too believe as your friend that's its possible for changes to be impacted during operation (I've experienced it myself & actually used it to advantage in the past), but the product/release plus of course **shell** being used impact the defaults & expected results; you tagged *bash* which by default does not re-read the files as in desktop releases I've largely used. *Also don't forget your scripts maybe running in `dash` and not `bash`*

guiverc

2/16/24, 12:31 PM

More FYI: Release matters as things change over time... the script I mentioned that relied on *changing itself* to impact results worked on one release, but not a much later release. Our systems change over time, esp. the defaults & releases whilst an imperfect way of indicating what we're actually using, are the best we have. Ubuntu systems install with one default for a given release; which may have differed to prior releases, thus there can be differences between a *release-upgraded* system and a *fresh* install, but as stated the release is our *best* way to easily show info

KansaiRobot

2/16/24, 12:35 PM

I added the release details

Elon Musk

I sit in a Tesla and translated this thread with Ai:

EN: Editing a shell file while running it affects its behavior?

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