YJL

A couple of years back I wrote about the builtin vs keyword conditional expressions, but I didnt think about another conditional use with arithmetic, that is with tests like [ $a -gt $b] or [[ $a -ne 0 ]].

Use similar code to benchmark 1 > 0 as shown below, not the real code, but you get the idea:

time for ((i = 0; i < 10000; i++)); do <test> 1 >/-gt 0 ; done

The result is:

(( is just marginally faster than [[ by my definition. Of course, they both are faster than builtin [ and test, as for /usr/bin/test, its an external command, there is no point to test, because its slow for sure.

With this result, there really isnt much difference between two, however, 1 > 0 is more readable than 1 -gt 0, literally and mathematically.

Even since I started writing Bash script, I always use [[ for if conditional statement, the double square brackets, never the single one version unless compatibility has to be taken into account. Why did I choose it? Its because I read [[ is faster. Ive never tried to confirm it by myself, although I do know that [ is a type of shell builtin command and [[ is type of shell keyword, and [ is equivalent to test, which is also a builtin command in Bash for very long time.¹

From time to time, I often see people still using [ even in the script with a few Bash-only syntaxes or features. They are clearly not writing with compatibility as a requirement. If I have a chance, then I would probably advise the coder to change to [[. I had done so a few times in the past.

However, I never see the numbers, so I used the following to test:

time for ((i = 0; i < 10000; i++)); do <test> -z '' ; done

The result is:

[ and test possibly are synonyms since they are pretty close.

As you can see [[ definitely is the winner, and /usr/bin/test external command is the slowest. The problem with /usr/bin/test isnt that is inefficient, but external command is costly.

If you are new to Bash, just use [[.