Eli Schwartz wrote: > 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
Should I change mine from a single [ ] to a double [[ ]]? For future compatibility if nothing else? Dale :-) :-)
