#!/usr/bin/env bash results in the script using whatever bash is found first in
While it is common for bash to be located at
/bin/bash. There are cases where it is not (different operating systems). Another potential use is when there are multiple bash shells installed (newer version at an alternate location like
#!/usr/bin/env bash just takes advantage of a behavior of the
env utility is normally used for manipulating the environment when calling a program (for example;
env -i someprog to wipe the environment clean). However by providing no arguments other than the program to execute, it results in executing the specified program as found in
Note that there are both advantages and disadvantages to doing this.
The advantages are as mentioned earlier, in that it makes the script portable if bash is installed in a different location, or if
/bin/bash is too old to support things the script is trying to do.
The disadvantage is that you can get unpredictable behavior. Since you're at the mercy of the user's
$PATH, it can result in the script being run with a version of bash that has different behavior than what the script expects.