^ in place of ! in glob bracket
expressions is undefined.echo foo-[^0]*.jpgecho foo-[!0]*.jpgor if the intention is to match ^ literally then either
do not put it immediately after [ or quote it by backslash
\
echo foo-[0^]*.jpg foo-[\^0]*.jpg[^c] is frequently used in most regular expression
variants to mean "any character except c". Ksh and Bash
adopted it for globs as well.
However, strictly speaking, the only range complement syntax
guaranteed to be supported across shells is [!c]. POSIX
explicitly states that behavior of [^c] is unspecified.
Dash used to support [^c] when compiled with
fnmatch and glob from glibc, but it was
considered as a bug
and fixed in version 0.5.12. Busybox has a similar bug 14516.
In zsh interactive sessions echo foo-[!0]*.jpg may cause
zsh: event not found: 0 error due to attempt of history
expansion. BASH however suppresses history expansion when !
is first character in square brackets.
Discrepancy of negation syntax in regular expressions and shell
pattern matching appeared in early UNIX versions. Pipeline syntax in
shells had not settled yet, some terminals had no | key, so
^ was used there. That is why in some shells exclamation
mark ! was chosen instead of circumflex (caret)
^ symbol for negation in globs. For more details related to
shell history see "The
^ = | ?" thread in the Unix
Heritage Society mailing list or Sven Mascheck. The
Traditional Bourne Shell Family. History and Development page.
If you only intend to target shells that supports this feature, you can change the shebang to a shell that guarantees support, or ignore this warning. Or just rewrite it to be on the technically correct side.
[^...] in addition to [!...] for
bracket expression negation POSIX enhancement request was
rejected.ShellCheck is a static analysis tool for shell scripts. This page is part of its documentation.