Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Defensive BASH programming

kfirlavi.com

Post reply on HN
Print view View original

21–30 of 53 posts

Re: Defensive BASH programming

#21

Post by vacri »

jakub_g wrote: post #19

Slightly off-topic but maybe some people will find it useful: I used to write my various glue-things-together scripts in bash, but this quickly becomes a nightmare as the script grows, due to bash's corner cases, syntax, portability issues etc. Recently I wrote my massive glue-things-together script with nodejs (since I already use node for many things) and it's much more maintainable and I couldn't be more happy. No…

Is it really a 'script' if you need to add a dir full of modules? I've always thought of 'scripts' as all-in-ones.

Re: Defensive BASH programming

#23

Post by c0l0 »

A guy publishing a guide for "defensive bash programming", who, in the process, provides this listing as an example for anything, is not fit for publishing said guide in the first place:

  main() {
      local files=$(ls /tmp | grep pid | grep -v daemon)
  }

Re: Defensive BASH programming

#24

Post by krallin »

catern wrote: post #20

The only thing in this post that can be accurately called defensive is the use of "local" and "readonly". The rest is all just style preferences, which are rather subjective, and none of which are very appealing to me. Three real defensive bash programming tips are: - Quote all uses of variables - set -o nounset - set -o errexit And many others can be found in and around http://mywiki.wooledge.org/BashFAQ

While not as common as nounset and errexit, pipefail is a useful option as well (set -o pipefail).

Using pipefail, if any program in a pipeline fails (i.e. exit code != 0), then the exit code for the pipeline will be != 0.

E.g. pipefail can be useful to ensure `curl does-not-exist-aaaaaaa.com | wc -c` doesn't exit with exit code 0..!

Re: Defensive BASH programming

#25

Post by Gnouc »

_ZeD_ wrote: post #14
ehartsuyker wrote: post #2

I think the best "defensive" piece of advice you left out that everyone abuses is never pipe `find` results to `xargs.` One should always do `find ... -print0` to a read-while loop because of filenames with whitespace.

avoid read-while loop... there are problems with filenames starting/ending with spaces... better use find ... -print0 | xargs -0 ... [eventually with -n1]

And you need non-standard feature `-print0` and `xargs -0` there. Better way should be `find ... -exec cmd {} +`.

Re: Defensive BASH programming

#26

Post by z3t4 »

jakub_g wrote: post #19

Slightly off-topic but maybe some people will find it useful: I used to write my various glue-things-together scripts in bash, but this quickly becomes a nightmare as the script grows, due to bash's corner cases, syntax, portability issues etc. Recently I wrote my massive glue-things-together script with nodejs (since I already use node for many things) and it's much more maintainable and I couldn't be more happy. No…

I would love to write my bash scripts in node, but end up writing them in bash anyway ... How do you do something like this in node?

  sudo -u 2>&1 >> logfile | tee | echo

Re: Defensive BASH programming

#27

Post by michaelhoffman »

krallin wrote: post #24
catern wrote: post #20

The only thing in this post that can be accurately called defensive is the use of "local" and "readonly". The rest is all just style preferences, which are rather subjective, and none of which are very appealing to me. Three real defensive bash programming tips are: - Quote all uses of variables - set -o nounset - set -o errexit And many others can be found in and around http://mywiki.wooledge.org/BashFAQ

While not as common as nounset and errexit, pipefail is a useful option as well (set -o pipefail). Using pipefail, if any program in a pipeline fails (i.e. exit code != 0), then the exit code for the pipeline will be != 0. E.g. pipefail can be useful to ensure `curl does-not-exist-aaaaaaa.com | wc -c` doesn't exit with exit code 0..!

You can set all three of them in a single line. Set up your Bash template with this today:

    set -o nounset -o pipefail -o errexit
Post reply on HN