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by initplus 1687 days ago
More serious than users fatfingering the command were scripts with code like

  rm -rf /$MYVAR
If you don't set $MYVAR and don't set bash to error on unset variables you are in for trouble.
2 comments
OJFord 1687 days ago
I don't recall which one it is (u for unset perhaps?) but I cover this by starting every (bash, E and pipefail are not POSIX) script with `set -eEuo pipefail`. All should be the default IMO, I don't understand - other than back-compat - why you wouldn't want them.
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SAI_Peregrinus 1687 days ago
It's -u.

You can also prevent this by never using $VAR, and instead always using ${VAR:?} to exit with error if VAR is unset (or use one of the other options to provide a default).

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andrewmackrodt 1686 days ago
A lesson I learnt several years ago when I discovered that mktemp behaves differently on macOS versus the GNU version in Linux.

From that day onward I always make sure the first line of my bash scripts contains at least "set -e".

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