I recently noticed that many scripts are using /usr/bin/env in their shebang. I have seen that mainly using Bash and Python, but thus far never in conjunction with POSIX sh (ash, dash,...).
I wonder why, and if my, meant-to-be highly portable, POSIX shell scripts might benefit from the env approach?
Is there a general concensus on whether to use:
standard:
#!/bin/sh
environment:
#!/usr/bin/env sh
Let me stress this enough:
I never have seen this with sh.
Setting to #!/bin/sh will go directly to that file /bin/sh.
Setting to #!/usr/bin/env sh will execute /usr/bin/env with an argument of sh. This will cause the script to be executed by sh in your PATH variable rather than explicitly with /bin/sh.
PATH is not the result from a getconf PATH call.
Many other posts (like the accepted answer of this one) mentioned that bin/sh in Solaris system (10 or older) is NOT a POSIX-compliant shell, instead, it is under /usr/xpg4/bin/sh.
In this case #!/bin/sh might not work properly if it meant to be POSIX-compliant. However, I doubt #!/usr/bin/env sh would point to the desired shell.
/bin/bashis an antiquated POC, but one can get newer bash via homebrew. So I use#!/usr/bin/env bashif write a script for both my MBP and my Linux PC. But if I'm going to stick to POSIX, then/bin/shis fine for both; I don't see much of a use case except in some outdated system where/bin/shmight not be a POSIX shell, in which case I doubt/usr/bin/envwill work either./bin/shand/usr/bin/env. Some obscure and mostly retired Unix variants had/bin/envwithout having/usr/bin/env, but you're unlikely to encounter them. Modern systems have/usr/bin/envprecisely because of its widespread use in shebangs./usr/bin/envis something you can count on."bashcompiled with default parameters is not POSIX compliant, this is why Apple offers a specialbashversion in/bin/shthat e.g. treatsechocorrectly. BTW:/bin/shis not part of POSIX. POSIX rather requires you to do:export PATH=$(getconf PATH)followed byshto get a POSIX shell./bin/sh. 2. Except for some obscure Chinese SUSE (or Centos?) fork(s) (iirc), no Linux system has ever been "certified" as Unix.