How can I mix [ ] single brackets and [[ ]] double brackets in the same if?

Question

I can't make this piece of code that uses single and double brackets work:

if [ ! $# == 1 ] && ! [[ $1 =~ ^[-]?[0-9]$ ]]; then exit 1 fi

How can I mix both single and double types in the same expression? Thanks.

You probably meant if [ "$#" -ne 1 ] || ! [[ $1 =~ ^-?[0123456789]$ ]]; then exit 1; fi which can also be written if [[ $# -ne 1 || ! $1 =~ ^-?[0123456789]$ ]]; then exit 1; fi. Or in standard sh: case $#:$1 in (1:[0123456789] | 1:-[0123456789]) ;; (*) exit 1; esac — Stéphane Chazelas
– Stéphane Chazelas, Commented May 25, 2022 at 19:18
The expression works fine but there is no valid reason to mix these. — jesse_b
– jesse_b, Commented May 25, 2022 at 19:19
Way easier indeed @StéphaneChazelas!! I am still learning bash.. Thank you. That was very helpful! — msmilkshake
– msmilkshake, Commented May 25, 2022 at 19:21

msmilkshake · Accepted Answer · 2022-05-25 19:28:54Z

1

Ok, with your help, I found a piece of code that works for my needs, no if needed. I used the following line:

[[ ! $# == 1 || ! $1 =~ ^-?[0-9]$ ]] && exit 1

Thank you all.

answered May 25, 2022 at 19:28

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