printf "%s\n" $pat

All shells appear to be in agreement that the backslash is taken literally here. It's treated as quoted, even though $pat is unquoted.


  case /dev in $pat) echo why ;; esac

Now, bash and dash say that the pattern does match -- they take the backslash as unquoted, allowing it to escape the v. Most other shells (bosh, ksh93, mksh, pdksh, posh, yash, zsh) still take the backslash as quoted.

This doesn't make sense to me, and doesn't match historic practice: dash before v0.5.5 took this backslash as quoted too. v0.5.5 then had some other related bugs that were fixed in v0.5.6, but it looks like an accident that this was not restored to the v0.5.4 behaviour.

This comes from expand.c's memtodest:

    if ((quotes & QUOTES_ESC) &&
        ((syntax[c] == CCTL) ||
         (((quotes & EXP_FULL) || syntax != BASESYNTAX) &&
          syntax[c] == CBACK)))
           USTPUTC(CTLESC, q);

This only escapes backslashes in field expansion context and in quoted string context. Should this simply be

    if ((quotes & QUOTES_ESC) &&
        ((syntax[c] == CCTL) || (syntax[c] == CBACK)))
           USTPUTC(CTLESC, q);

or are there scenarios where it's important to treat an expanded backslash as unquoted?

Harald van Dijk
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