-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 According to [EMAIL PROTECTED] on 1/6/2006 3:02 PM: > > [EMAIL PROTECTED]:~$ touch testFile > [EMAIL PROTECTED]:~$ [ -a testFile ] && echo true || echo false > true
POSIX requires (http://www.opengroup.org/onlinepubs/009695399/utilities/test.html) that a test with two arguments (in your case, "-a" and "testFile") produce unspecified results if the first is neither "!" nor a unary primary. "-a" is not a required POSIX unary operator. So bash is in its right to return whatever it wants; in this case, bash has the extension that "-a" is also a unary operator, returning 0 if file exists (contrast that with coreutils' /bin/test, which does not have a unary -a, so it currently returns 1, although it would also be valid for coreutils to print an error message that an unknown unary operator was encountered and return 2). > > [EMAIL PROTECTED]:~$ [ ! -a testFile ] && echo true || echo false > true Now, in this case, you have three arguments, and POSIX requires that the binary operator "-a" have higher precedence than the "!" negation operator on a 2-argument test. And the one-argument test of "!" and of "testFile" both return true (since neither is the empty string), so the overall expression returns 0. You are probably better off using the unary operator -e for file existance rather than -a. Also, be aware that bash also defines a unary -o, so the following also has strange results, for the same reasons as above: $ set -o monitor $ rm -f monitor $ test -o monitor && echo true true $ test ! -o monitor && echo true true - -- Life is short - so eat dessert first! Eric Blake [EMAIL PROTECTED] -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.1 (Cygwin) Comment: Public key at home.comcast.net/~ericblake/eblake.gpg Comment: Using GnuPG with Thunderbird - http://enigmail.mozdev.org iD8DBQFDv9t084KuGfSFAYARAmpVAJsF+DGBDWhubt2hNB4aVgNMuhTsbgCgliGS dtP5QKjRVthlW5zcgKcGy00= =28b8 -----END PGP SIGNATURE----- _______________________________________________ Bug-bash mailing list Bug-bash@gnu.org http://lists.gnu.org/mailman/listinfo/bug-bash
