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I'm looking at a shell script that contains the following:

set +e
set -x

I see that the commands are used to "assign a value to a shell variable". But in this context I don't understand the usage.

https://afni.nimh.nih.gov/pub../pub/dist/edu/data/CD.expanded/AFNI_data6/unix_tutorial/misc/unix_commands.html#set

1 Answer 1

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That style of set command sets or unsets shell options. Confusingly - sets the option and + unsets the option.

option e makes the shell script error out whenever a command errors out. It's generally a good idea to have it enabled most of the time.

option x makes the shell print out commands after expanding their parameters but before executing them. Useful when debugging but can get overwhelming sometimes.

See https://www.gnu.org/software/bash/manual/html_node/The-Set-Builtin.html for more (that documentation is for bash but many of the features are common across many shells)

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