Обсуждение: PQescapeLiteral in Libpq
I'm using the libpq.dll libraries to connect to postgress. When I issue a call to PQescapeLiteral with a file path as the argument, the result string seems to always start with a bogus " E". For example, "C:\MyFile" is returned as " E'C:\\:MyFile'" (not including the double quotes). Is this a normal result or can't PQescapeLiteral be used to escape a file path literal? If not, are there any functions that can be used to "escape" a file path?
Thanks, Lynn
"lmanorders" <lmanorders@gmail.com> writes:
> I'm using the libpq.dll libraries to connect to postgress. When I issue a call to PQescapeLiteral with a file path as
theargument, the result string seems to always start with a bogus " E".
That's not bogus, it's the intended behavior. Per the source code:
* If we are escaping a literal that contains backslashes, we use the
* escape string syntax so that the result is correct under either value
* of standard_conforming_strings. We also emit a leading space in this
* case, to guard against the possibility that the result might be
* interpolated immediately following an identifier.
regards, tom lane
lmanorders wrote > I'm using the libpq.dll libraries to connect to postgress. When I issue a > call to PQescapeLiteral with a file path as the argument, the result > string seems to always start with a bogus " E". For example, "C:\MyFile" > is returned as " E'C:\\:MyFile'" (not including the double quotes). Is > this a normal result or can't PQescapeLiteral be used to escape a file > path literal? If not, are there any functions that can be used to "escape" > a file path? > > Thanks, Lynn What do you expect it to give in this instance? I don't get why there is an extra colon in your output (typo on your part?) but the "E" and the double-backslash are present because the "E" converts the literal into one that accepts escape sequences (of the form backslash-something, e.g., \n for a newline). Since backslash is an escape indicator in order to output a literal "\" you have to double/escape it "\\". David J. -- View this message in context: http://postgresql.1045698.n5.nabble.com/PQescapeLiteral-in-Libpq-tp5786141p5786147.html Sent from the PostgreSQL - novice mailing list archive at Nabble.com.
----- Original Message ----- From: "David Johnston" <polobo@yahoo.com> To: <pgsql-novice@postgresql.org> Sent: Thursday, January 09, 2014 12:35 PM Subject: Re: [NOVICE] PQescapeLiteral in Libpq > lmanorders wrote >> I'm using the libpq.dll libraries to connect to postgress. When I issue a >> call to PQescapeLiteral with a file path as the argument, the result >> string seems to always start with a bogus " E". For example, "C:\MyFile" >> is returned as " E'C:\\:MyFile'" (not including the double quotes). Is >> this a normal result or can't PQescapeLiteral be used to escape a file >> path literal? If not, are there any functions that can be used to >> "escape" >> a file path? >> >> Thanks, Lynn > > What do you expect it to give in this instance? I didn't expect the " E" in front of the literal. > > I don't get why there is an extra colon in your output (typo on your > part?) > but the "E" and the double-backslash are present because the "E" converts > the literal into one that accepts escape sequences (of the form > backslash-something, e.g., \n for a newline). Since backslash is an > escape > indicator in order to output a literal "\" you have to double/escape it > "\\". The second colon is a typo. I did expect the "\" to be doubled, just not the leading " E" in the result. Thanks for the quick responses! > > David J. > > > > > -- > View this message in context: > http://postgresql.1045698.n5.nabble.com/PQescapeLiteral-in-Libpq-tp5786141p5786147.html > Sent from the PostgreSQL - novice mailing list archive at Nabble.com. > > > -- > Sent via pgsql-novice mailing list (pgsql-novice@postgresql.org) > To make changes to your subscription: > http://www.postgresql.org/mailpref/pgsql-novice >