On 7/1/25 10:41 PM, Grant Edwards wrote: > On 2025-07-02, Eli Schwartz <eschwa...@gentoo.org> wrote: > >> if [ "$?" -eq "0" ] ; then >> echo "Crypt file system is open" >> else >> echo "Crypt is not open. Please enter passphrase." >> cryptsetup open $LVM_DEV crypt >> fi >> >> This makes your eyes get drawn to the lines that are aligned left, which >> have the "when shall I run it?" logic. You can easily tell that >> "cryptsetup open" happens AFTER the "else". > > Maybe it's just me, but I've switched from using [ ] to [[ ]]. I find > it works right the first try way more often. It's a bash built-in, and > the quoting and whitespace handling seems to work more like my brain > expects. After decades of using [ ], I was still regularly tripped up > in ways that I don't seem to be using [[ ]].
Yes, in general [[ is better than [ The practical difference is that it is parsed as a keyword, not as an ordinary command, hence it knows what is inside of it without whitespace handling. i.e. [[ $FOO = bar ]] $FOO does not need quotes because [[ runs *before* word splitting. It also supports regex! $ FOO="something" $ [[ $FOO =~ ^s(.*)e(.*)n ]] $ declare -p BASH_REMATCH declare -a BASH_REMATCH=([0]="somethin" [1]="om" [2]="thi") It's very powerful and purely additive over [ But it doesn't matter when pointing out how bash does whitespace splitting of commands. :) > [And it's even support > by busybox's ash shell.] Beware that busybox ash supports [[ "partially". From the busybox source code comments: /* BASH_TEST2: [[ EXPR ]] * Status of [[ support: * && and || work as they should * = is glob match operator, not equality operator: STR = GLOB * == same as = * =~ is regex match operator: STR =~ REGEX * TODO: * singleword+noglob expansion: * v='a b'; [[ $v = 'a b' ]]; echo 0:$? * [[ /bin/n* ]]; echo 0:$? * quoting needs to be considered (-f is an operator, "-f" and ""-f are not; etc) * ( ) < > should not have special meaning (IOW: should not require quoting) * in word = GLOB, quoting should be significant on char-by-char basis: a*cd"*" */ #define BASH_TEST2 (ENABLE_ASH_BASH_COMPAT * ENABLE_ASH_TEST) -- Eli Schwartz
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