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August 29, 2015 13:56
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A protip for authors of shell programs. I use this pattern *all the time* for working in a temporary directory and cleaning it up after I'm done but a quirk in how shells interpret failures in command substitution caused a program like these to remove my coworker's home directory when he ran said program on Mac OS X, which doesn't have `mktemp -d`.
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| set -e | |
| # Looks clever, is short, but removes your working directory on Mac OS X | |
| # where `mktemp -d` fails. | |
| cd "$(mktemp -d)" | |
| trap "rm -rf \"$PWD\"" EXIT INT QUIT TERM | |
| # ... |
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| set -e | |
| # Is longer, is named terribly, but at least it doesn't fail by removing | |
| # your home directory. | |
| TMP="$(mktemp -d)" | |
| cd "$TMP" | |
| trap "rm -rf \"$TMP\"" EXIT INT QUIT TERM | |
| # ... |
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OS X has had
mktemp -dfor a long time (2005?) but it's the BSD variant which requires a template argument to-d:That said, this is a great general cautionary point – there's no reason not to use the second form worth the risk of getting it wrong.