On Thu, Aug 25, 2022 at 03:32:15PM +0200, Laszlo Ersek wrote: > Hi, > > most shell scripts in the v2v projects start with a shebang like this: > > #!/bin/bash - > > I *think* I understand the intent of the single hyphen, but (a) it seems > unnecessary, (b) even if we insisted, using the double-hyphen separator "--" > is much more idiomatic (even though the shell, per POSIX, is supposed to > interpret "-" identically to "--"). > > Regarding why I think the hyphen is unnecessary: > > - setuid shell scripts are not a thing on any platform we (should) care about > > - the script name is not reinterpreted as an option *anyway* > > Consider: > > cat >-v <<EOT > #!/bin/bash > echo hello \$1 > EOT > > chmod +x -- -v > > PATH=$PWD:$PATH -v world > --> hello world > > That is, when we run the script under the name "-v" (with it being on the > PATH) and with the single command line argument "world", we'd naively asume > that the shebang translated to: > > /bin/bash -v world > > where "-v" came from the script's name, and "world" would be taken as the > name of a shell script to execute. Thus, the idea would be to prevent this > (i.e., to pass options to the interpreter by renaming or (sym)linking the > shell script). > > But that's not what we actually see; what we see is consistent with the > command: > > /bin/bash -- -v world > --> hello world > > In fact, if I append "sleep 1000" to the script, I can also fetch: > > $ hexdump -C /proc/10975/cmdline > 00000000 62 61 73 68 00 2d 2d 00 2d 76 00 77 6f 72 6c 64 |bash.--.-v.world| > 00000010 00 |.| > 00000011 > > So glibc and/or the Linux kernel already inserts the "--" option/operand > delimiter! > > I intend to contribute a shell script to virt-p2v; do I need to use the > hyphen in the shebang? (If so, I prefer the double-hyphen.)
Eric should be able to give the definitive answer here. Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com virt-top is 'top' for virtual machines. Tiny program with many powerful monitoring features, net stats, disk stats, logging, etc. http://people.redhat.com/~rjones/virt-top _______________________________________________ Libguestfs mailing list Libguestfs@redhat.com https://listman.redhat.com/mailman/listinfo/libguestfs
