On Fri, Aug 26, 2022 at 01:37:37PM +0100, Richard W.M. Jones wrote: > > > > Shebang interpretation is sometimes by the kernel, and sometimes by > > the shell, and it differs by OS. Some OS's do word-splitting on the > > rest of the shebang after the first space, some treat the entire rest > > of the line as a single argument. > > > > For a nice summary of some of the warts of shebang lines, see > > > > https://unix.stackexchange.com/questions/29608/why-is-it-better-to-use-usr-bin-env-name-instead-of-path-to-name-as-my/29620#29620 > > > > If you are worried about /bin/bash being available on all systems > > where a v2v script will be installed, you probably want '#!/bin/env > > bash' to find the first bash in PATH. But once you add your first > > whitespace, it is no longer portable to use any others, so while > > '#!/bin/bash -' works, '#!/bin/env bash -' does not. I find that the > > issue of writing a shebang to use a program that may not always be > > installed in the same absolute location across all OSs (and therefore > > where '#!/bin/env name' is useful) is more common than the issue of > > writing a shebang that wants to pass an explicit '-' or '--' > > end-of-option marker to protect against the script being installed > > under a name like '-c ls'. > > Fedora packaging guidelines -- rightly or wrongly -- forbid #!/usr/bin/env: > > https://docs.fedoraproject.org/en-US/packaging-guidelines/#_shebang_lines > > although apparently RPM rewrites them automatically so perhaps we > would not notice.
Yeah, for an executable installed as part of the system, you really DO want it hard-coded to the interpreter also installed by the system (because that's what was integration-tested), and not using env (which is dependent on the user's environment on whether it behaves the same or picks a different interpreter than what the system integration-tested). It's a good policy for the RPM, but less so for scripts that are not installed as part of a single system (that is, scripts in $HOME/bin that is network-mounted across multiple different OSs is very much a good place to use #!/bin/env). -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3266 Virtualization: qemu.org | libvirt.org _______________________________________________ Libguestfs mailing list Libguestfs@redhat.com https://listman.redhat.com/mailman/listinfo/libguestfs
