Help with Command Substitution in Bash Script

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Asked By TechJunky79 On

I've been battling a command substitution issue in my bash script that's driving me nuts! I have a binary that I need to execute, but it sometimes fails, and when it does, I need to run it in a chroot environment for further operations. So, if the binary fails, I set a variable called RUN_IN_CHROOT to 'yes'. I'm capturing the output using command substitution, as shown:

MY_BINARY=/path/to/binary
mode=$(${MY_BINARY} -m $param1)

If the first command fails, I set RUN_IN_CHROOT to 'yes' and then try to run it in chroot:

mode=$(${RUN_IN_CHROOT:+chroot} ${RUN_IN_CHROOT:+/mnt} ${MY_BINARY} -m $param1)

However, I'm running into this error: 'chroot /mnt: No such file or directory.' It seems to be treating 'chroot /mnt' as a single command. When I run the script with 'bash -x', I see it trying to execute 'chroot /mnt' /path/to/binary -m 8, which isn't working the way I planned. Any ideas on why this is happening and how I can fix it? By the way, I figured out the issue was due to IFS being set incorrectly, and resetting it solved the problem!

5 Answers

Answered By DebugQueen On

Have you tried using 'set -x' to debug? Also, chroot needs to be run by the root user—are you certain it's being executed with the right permissions? Just checking because the error suggests it might not be.

Answered By BashGuru99 On

Can you share the exact script you're working on? Often, these bizarre errors come from something small that's missing in the post. Seeing the whole picture could help track down the issue.

Answered By HelpfulHank On

For anyone else who checks this thread later, I just want to clarify: a non-standard IFS value wouldn’t cause the specific error OP mentioned. They likely mistyped the command somewhere. Using functions could simplify your code and make it easier to read.

Answered By ScriptHelper23 On

It would help if you could paste your script here to allow others to test it locally and help troubleshoot the problem.

Answered By FixItFrank On

Sometimes, hitting the space bar with the Alt Gr key can insert a non-breaking space instead of a regular space, causing issues. Double-check that you haven’t accidentally typed one!

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