4 ms·

> All the cleverness and precedence rules in the article seem to ignore the fundamental problem: the test and [ binaries are regular programs, and they cannot d

by rascul 4y ago

> All the cleverness and precedence rules in the article seem to ignore the fundamental problem: the test and [ binaries are regular programs, and they cannot distinguish between an argument that looks like “(“ and (. In both cases, they get the string “(“ in argv. Regular programs can make that distinction with no problem, the mistake is thinking that the outer quotes are part of the argument. In the context of the POSIX style shell, they're not, they signify that what is enclosed is one argument. So you'll have to use one of the various mechanisms the shell provides to indicate that you want to pass the quotes as an argument.

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Sophira 4y ago
I'm not the person you replied to, but I was unaware of the fact that it was possible to tell the difference between the arguments ( and "(" in a regular program. May I ask how? My understanding was that the shell stripped the quotes before it ever reached the program (and that the only method of bypassing that would have been to escape the quotes or enclose the argument in single quotes, for example).
- rascul 4y ago
  $ echo "(" '"("' ( "(" "(" the argument is ( '"("' the argument is "(" When you inspect argv in your program, you will see the argument including the quotes in the second example.
  - Sophira 4y ago
    Ah yes, that's what I meant by putting the argument in single quotes. I thought you were saying that the statement 'In both cases, they get the string “(“ in argv.' wasn't necessarily true. My apologies!
a1369209993 4y ago
> the mistake is thinking that the outer quotes are part of the argument. > you want to pass the quotes as an argument. Yes, that's the point - in the context of /bin/[, 'x' is the quote; that's how you quote string arguments to [. (Yes, it's ad hoc as hell; that's fairly par for the course for unix.)
- rascul 4y ago
  I don't get what you're saying. x isn't the quote, it's made to be part of the string being matched, to catch edge cases. You don't need to understand quoting rules to pass 'x' as an argument as you would '"("'.

by rascul 4y ago

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Sophira 4y ago

I'm not the person you replied to, but I was unaware of the fact that it was possible to tell the difference between the arguments ( and "(" in a regular program. May I ask how? My understanding was that the shell stripped the quotes before it ever reached the program (and that the only method of bypassing that would have been to escape the quotes or enclose the argument in single quotes, for example).

rascul 4y ago
$ echo "(" '"("' ( "(" "(" the argument is ( '"("' the argument is "(" When you inspect argv in your program, you will see the argument including the quotes in the second example.
- Sophira 4y ago
  Ah yes, that's what I meant by putting the argument in single quotes. I thought you were saying that the statement 'In both cases, they get the string “(“ in argv.' wasn't necessarily true. My apologies!

a1369209993 4y ago

> the mistake is thinking that the outer quotes are part of the argument. > you want to pass the quotes as an argument. Yes, that's the point - in the context of /bin/[, 'x' is the quote; that's how you quote string arguments to [. (Yes, it's ad hoc as hell; that's fairly par for the course for unix.)

rascul 4y ago
I don't get what you're saying. x isn't the quote, it's made to be part of the string being matched, to catch edge cases. You don't need to understand quoting rules to pass 'x' as an argument as you would '"("'.