Thanks, Ian!
--
Maxim Kuvyrkov
https://www.linaro.org
> On Mar 8, 2023, at 2:51 PM, Ian Abbott <abbo...@mev.co.uk> wrote:
>
> On 07/03/2023 18:40, Maxim Kuvyrkov wrote:
>> Hi Bash Experts!
>> Every couple of years I stumble upon weird behavior in bash scripts, which I
>> cannot explain, and every time it was due to documented bash behavior. Can,
>> please, someone explain to me why the following script terminates?
>> I've tried this on Ubuntu 22.04 and Ubuntu 20.04 with same results -- see
>> "Observations" at the end of the script.
>> Thanks!
>> ===
>> #!/bin/bash
>> set -euf -o pipefail
>> print_test ()
>> {
>> local count="$1"
>> while [ $count -ge 0 ]; do
>> if [ x"$(echo a)" = x"a" ]; then
>> echo a
>> fi
>> count=$(($count - 1))
>> done
>> }
>> main ()
>> {
>> local count=1
>> while print_test "$count" | grep -q "a"; do
>> echo "$count: OK"
>> count=$(($count + 1))
>> done
>> echo "$count: BAD"
>> }
>> main
>> exit 1
>> # Observations:
>> # 1. With "if" in print_test BAD happens on around count "2"
>> # 2. Without "if" in print_test BAD happens around count "80"
>> # 3. Changing "grep -q" to "grep" makes the problem go away.
>> # 4. Removing -o pipefail makes the problem go away.
>> # 5. While loop in "main" isn't required, but makes reproduction easier.
>> ===
>> --
>> Maxim Kuvyrkov
>> https://www.linaro.org
>
> grep -q is exiting as soon as a match is found. print_test is continuing to
> write to the now-broken pipe and gets killed by a SIGPIPE.
>
> --
> -=( Ian Abbott <abbo...@mev.co.uk> || MEV Ltd. is a company )=-
> -=( registered in England & Wales. Regd. number: 02862268. )=-
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>
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