On Thu, Apr 06, 2023 at 04:43:51AM +0000, Fergus Daly via Cygwin wrote: > I have a "hash bang" bash shell script i.e. first line > #! /bin/sh > or equivalently > #! /bin/bash > For various reasons I want this file to be identified as binary so its second > line > is the single character null \x00 showing up in some editors e.g. nano as > ^@ > This does not prevent the script from running to a successful conclusion. > Or not until recently. Now the script fails with > /home/user/bin/file.old.sh: cannot execute binary file > Q1 - was bash recently updated? Would this explain the changed behaviour? > Q2 - if so, is this newly introduced "glitch" known and presumably intended? > Or > an unintended consequence that will be retracted in a later update? > I then altered the first line to > #! /bin/dash > whilst retaining the null character at line 2 and subsequent content also > unaltered.. > The altered script file.new.sh runs as previously to a successful conclusion. > Q3 - at 1/8 the size of bash and sh, I am not at all sure of the role and > reach of dash. > Should the edit (dash replacing bash/sh) be incorporated elsewhere or would > this be a > bad idea (and retained only locally in what is indeed an eccentric and > one-off context)?
Dash is smaller and much less feature-rich than Bash. Whether Dash is a suitable replacement for Bash depends on how much (if at all) you're relying on Bash-specific functions. For very simple scripts, the only difference is likely that Dash will be very slightly faster, but working out whether your script is using any "Bashisms" isn't always a trivial job. (I have previously been involved work in migrating scripts between Ksh and Bash, which is a similar-but-different problem, and there were *a lot* of surprises in how the two differed.) Depending on why you want the file to be identified as a binary, and how that identification is being done, you could move your null byte later in the file. In particular, a pattern I've seen several times in Bash is to have a normal Bash script, finishing with an explicit `exit`, followed by an actual binary blob; this can be used to create things like self-extracting bundles, where the binary blob is a tarball and the script at the top of the file has the instructions for extracting the tarball. -- Problem reports: https://cygwin.com/problems.html FAQ: https://cygwin.com/faq/ Documentation: https://cygwin.com/docs.html Unsubscribe info: https://cygwin.com/ml/#unsubscribe-simple
