Обсуждение: psql man page error?
On the psql man page there is an example of how to perform multiple line
psql script as part of the -c option description.
The example given is
echo "\x \\ select * from foo;" | psql
which gives
prompt> echo "\x \\ select * from foo;" | psql
Expanded display is on.
invalid command \
i.e. doesn't work on bash. With bash the command should be:
echo -e "\x \n select * from foo;" | psql
which gives
prompt> echo -e "\x \n select * from foo;" | psql
Expanded display is on.
ERROR: relation "foo" does not exist
Does this mean there are multiple forms of the echo command, or is this
example just wrong?
--
Simon Riggs
EnterpriseDB http://www.enterprisedb.com
On Tue, 5 Dec 2006, Simon Riggs wrote: > which gives > > prompt> echo "\x \\ select * from foo;" | psql > Expanded display is on. > invalid command \ > > i.e. doesn't work on bash. With bash the command should be: > > echo -e "\x \n select * from foo;" | psql > > which gives > > prompt> echo -e "\x \n select * from foo;" | psql > Expanded display is on. > ERROR: relation "foo" does not exist > > Does this mean there are multiple forms of the echo command, or is this > example just wrong? I believe that /bin/echo and the bash built-in used to be slightly different, although reviewing both man pages on my FC5 system seem to indicate that they have the same command-line arguments. It's also possible that I'm thinking back to my Solaris (2.5.1) days when the built-in tcsh echo was in fact different than /bin/echo. That's why all my scripts seem to call the binary and not the built-in. Another possibility is that the original author had the options set in his xpg_echo environment variable and forgot about it...or his distro was setting it in a profile.d file. -- Jeff Frost, Owner <jeff@frostconsultingllc.com> Frost Consulting, LLC http://www.frostconsultingllc.com/ Phone: 650-780-7908 FAX: 650-649-1954
Simon Riggs wrote:
>
> On the psql man page there is an example of how to perform multiple line
> psql script as part of the -c option description.
>
> The example given is
>
> echo "\x \\ select * from foo;" | psql
>
> which gives
>
> prompt> echo "\x \\ select * from foo;" | psql
> Expanded display is on.
> invalid command \
>
> i.e. doesn't work on bash. With bash the command should be:
>
> echo -e "\x \n select * from foo;" | psql
>
> which gives
>
> prompt> echo -e "\x \n select * from foo;" | psql
> Expanded display is on.
> ERROR: relation "foo" does not exist
>
> Does this mean there are multiple forms of the echo command, or is this
> example just wrong?
Intersting. This example has been around since at least 2002. The SGML
looks like this:
<application>psql</application>, like this: <literal>echo "\x \\
select * from foo;" | psql</literal>.
and I suppose the asumption was that the \\ would be at the end of the
output line, but in fact both HTML and manual pages just put the \\
anywhere on the line. I think the proper fix is:
<application>psql</application>, like this: <literal>echo -e
"\\x\nSELECT * FROM foo;" | psql</literal>.
I think all modern operating systems understand echo -e at this point.
Change applied to HEAD and 8.2.X.
--
Bruce Momjian bruce@momjian.us
EnterpriseDB http://www.enterprisedb.com
+ If your life is a hard drive, Christ can be your backup. +
Bruce Momjian <bruce@momjian.us> writes: > I think the proper fix is: > <application>psql</application>, like this: <literal>echo -e > "\\x\nSELECT * FROM foo;" | psql</literal>. > I think all modern operating systems understand echo -e at this point. No, they don't, and neither does the Single Unix Spec: http://www.opengroup.org/onlinepubs/007908799/xcu/echo.html So your version of the example depends on non-standards-compliant echo behavior, which is not better than before. regards, tom lane
On Tue, 2006-12-05 at 13:14 -0500, Tom Lane wrote: > Bruce Momjian <bruce@momjian.us> writes: > > I think the proper fix is: > > > <application>psql</application>, like this: <literal>echo -e > > "\\x\nSELECT * FROM foo;" | psql</literal>. > > > I think all modern operating systems understand echo -e at this point. > > No, they don't, and neither does the Single Unix Spec: > http://www.opengroup.org/onlinepubs/007908799/xcu/echo.html > > So your version of the example depends on non-standards-compliant > echo behavior, which is not better than before. So the -e is wrong, but the rest of the change was right. Guess we just need to add a comment about "(you may need to use the -e option on echo to get this to work on your OS)." -- Simon Riggs EnterpriseDB http://www.enterprisedb.com
Tom Lane wrote: > Bruce Momjian <bruce@momjian.us> writes: > > I think the proper fix is: > > > <application>psql</application>, like this: <literal>echo -e > > "\\x\nSELECT * FROM foo;" | psql</literal>. > > > I think all modern operating systems understand echo -e at this point. > > No, they don't, and neither does the Single Unix Spec: > http://www.opengroup.org/onlinepubs/007908799/xcu/echo.html > > So your version of the example depends on non-standards-compliant > echo behavior, which is not better than before. Well, at least my example works on _some_ operating systems, while the previous worked on none of them, so it is _better_. I can't think of a good way to do this except converting the example to a <programlisting> block that will not change newlines: echo '\x SELECT * FROM foo;' | psql Is that what people want? -- Bruce Momjian bruce@momjian.us EnterpriseDB http://www.enterprisedb.com + If your life is a hard drive, Christ can be your backup. +
On Tue, 2006-12-05 at 18:16 -0500, Bruce Momjian wrote: > Tom Lane wrote: > > Bruce Momjian <bruce@momjian.us> writes: > > > I think the proper fix is: > > > > > <application>psql</application>, like this: <literal>echo -e > > > "\\x\nSELECT * FROM foo;" | psql</literal>. > > > > > I think all modern operating systems understand echo -e at this point. > > > > No, they don't, and neither does the Single Unix Spec: > > http://www.opengroup.org/onlinepubs/007908799/xcu/echo.html > > > > So your version of the example depends on non-standards-compliant > > echo behavior, which is not better than before. > > Well, at least my example works on _some_ operating systems, while the > previous worked on none of them, so it is _better_. > > I can't think of a good way to do this except converting the example to > a <programlisting> block that will not change newlines: > > echo '\x > SELECT * FROM foo;' | psql > > Is that what people want? Well, it works, but IMHO its not as clear. -- Simon Riggs EnterpriseDB http://www.enterprisedb.com
Simon Riggs wrote: > On Tue, 2006-12-05 at 18:16 -0500, Bruce Momjian wrote: > > Tom Lane wrote: > > > Bruce Momjian <bruce@momjian.us> writes: > > > > I think the proper fix is: > > > > > > > <application>psql</application>, like this: <literal>echo -e > > > > "\\x\nSELECT * FROM foo;" | psql</literal>. > > > > > > > I think all modern operating systems understand echo -e at this point. > > > > > > No, they don't, and neither does the Single Unix Spec: > > > http://www.opengroup.org/onlinepubs/007908799/xcu/echo.html > > > > > > So your version of the example depends on non-standards-compliant > > > echo behavior, which is not better than before. > > > > Well, at least my example works on _some_ operating systems, while the > > previous worked on none of them, so it is _better_. > > > > I can't think of a good way to do this except converting the example to > > a <programlisting> block that will not change newlines: > > > > echo '\x > > SELECT * FROM foo;' | psql > > > > Is that what people want? > > Well, it works, but IMHO its not as clear. Well, it is even worse because some versions of echo automatically interpret backslashes, so it would have to be \\x. I am thinking we should just leave it as I have it now, unless we want to use 'awk' or 'perl' where we know the backslash behavior. -- Bruce Momjian bruce@momjian.us EnterpriseDB http://www.enterprisedb.com + If your life is a hard drive, Christ can be your backup. +
Bruce Momjian <bruce@momjian.us> writes:
> Well, it is even worse because some versions of echo automatically
> interpret backslashes, so it would have to be \\x. I am thinking we
> should just leave it as I have it now, unless we want to use 'awk' or
> 'perl' where we know the backslash behavior.
The example as you have it now is directly contradictory to the
published spec.
I agree with Simon's suggestion to remove "-e" from the example
(thereby making it spec-compliant) and add a parenthetical remark
suggesting that standards-challenged versions of echo might need "-e".
regards, tom lane
Am Dienstag, 5. Dezember 2006 18:41 schrieb Bruce Momjian: > <application>psql</application>, like this: <literal>echo "\x \\ > select * from foo;" | psql</literal>. > > and I suppose the asumption was that the \\ would be at the end of the > output line, but in fact both HTML and manual pages just put the \\ > anywhere on the line. Which is correct. Removing the \\ alters the point of the example. -- Peter Eisentraut http://developer.postgresql.org/~petere/
Peter Eisentraut wrote: > Am Dienstag, 5. Dezember 2006 18:41 schrieb Bruce Momjian: > > <application>psql</application>, like this: <literal>echo "\x \\ > > select * from foo;" | psql</literal>. > > > > and I suppose the asumption was that the \\ would be at the end of the > > output line, but in fact both HTML and manual pages just put the \\ > > anywhere on the line. > > Which is correct. Removing the \\ alters the point of the example. Well, if it doesn't render \\ at the end of the line, the example isn't very clear unless you are looking at the SGML. -- Bruce Momjian bruce@momjian.us EnterpriseDB http://www.enterprisedb.com + If your life is a hard drive, Christ can be your backup. +
Tom Lane wrote: > Bruce Momjian <bruce@momjian.us> writes: > > Well, it is even worse because some versions of echo automatically > > interpret backslashes, so it would have to be \\x. I am thinking we > > should just leave it as I have it now, unless we want to use 'awk' or > > 'perl' where we know the backslash behavior. > > The example as you have it now is directly contradictory to the > published spec. > > I agree with Simon's suggestion to remove "-e" from the example > (thereby making it spec-compliant) and add a parenthetical remark > suggesting that standards-challenged versions of echo might need "-e". Well, I just tried Linux and FreeBSD bash (the default shell?) and they both need '-e' to render '\n' as a newline, so I think we should just leave it with '-e'. Following the spec doesn't help if our two major operating systems don't follow the spec, plus the example doesn't work on Win32 at all. -- Bruce Momjian bruce@momjian.us EnterpriseDB http://www.enterprisedb.com + If your life is a hard drive, Christ can be your backup. +
Bruce Momjian <bruce@momjian.us> writes:
> Peter Eisentraut wrote:
>> Which is correct. Removing the \\ alters the point of the example.
> Well, if it doesn't render \\ at the end of the line, the example isn't
> very clear unless you are looking at the SGML.
No, you've completely misunderstood the original example. It's
intending to show a backslash-backslash terminator for the \x command,
not two lines of input, ie the equivalent of this:
regression=# \x \\ select 1,2;
Expanded display is on.
-[ RECORD 1 ]
?column? | 1
?column? | 2
regards, tom lane
On Wed, Dec 06, 2006 at 09:14:01 -0500, Bruce Momjian <bruce@momjian.us> wrote: > > Well, I just tried Linux and FreeBSD bash (the default shell?) and they > both need '-e' to render '\n' as a newline, so I think we should just > leave it with '-e'. Following the spec doesn't help if our two major > operating systems don't follow the spec, plus the example doesn't work > on Win32 at all. If you need several lines of output, couldn't you use one echo for each line and separate them with semicolons?
Tom Lane wrote: > Bruce Momjian <bruce@momjian.us> writes: > > Peter Eisentraut wrote: > >> Which is correct. Removing the \\ alters the point of the example. > > > Well, if it doesn't render \\ at the end of the line, the example isn't > > very clear unless you are looking at the SGML. > > No, you've completely misunderstood the original example. It's > intending to show a backslash-backslash terminator for the \x command, > not two lines of input, ie the equivalent of this: > > regression=# \x \\ select 1,2; > Expanded display is on. > -[ RECORD 1 ] > ?column? | 1 > ?column? | 2 You are right, I totally misunderstood it. New patch applied, that mentions \\ is a separator meta-command. I now see \\ documented farther down the file. I didn't know it did that. -- Bruce Momjian bruce@momjian.us EnterpriseDB http://www.enterprisedb.com + If your life is a hard drive, Christ can be your backup. + Index: doc/src/sgml/ref/psql-ref.sgml =================================================================== RCS file: /cvsroot/pgsql/doc/src/sgml/ref/psql-ref.sgml,v retrieving revision 1.176 diff -c -c -r1.176 psql-ref.sgml *** doc/src/sgml/ref/psql-ref.sgml 5 Dec 2006 17:40:55 -0000 1.176 --- doc/src/sgml/ref/psql-ref.sgml 6 Dec 2006 15:37:30 -0000 *************** *** 87,95 **** it contains no <application>psql</application> specific features), or a single backslash command. Thus you cannot mix <acronym>SQL</acronym> and <application>psql</application> ! meta-commands. To achieve that, you could pipe the string into ! <application>psql</application>, like this: <literal>echo -e ! "\\x\nSELECT * FROM foo;" | psql</literal>. </para> <para> If the command string contains multiple SQL commands, they are --- 87,96 ---- it contains no <application>psql</application> specific features), or a single backslash command. Thus you cannot mix <acronym>SQL</acronym> and <application>psql</application> ! meta-commands with this option. To achieve that, you could ! pipe the string into <application>psql</application>, like ! this: <literal>echo "\x \\ SELECT * FROM foo;" | psql</literal>. ! (<literal>\\</> is the separator meta-command.) </para> <para> If the command string contains multiple SQL commands, they are
Bruce Momjian <bruce@momjian.us> writes:
> ! pipe the string into <application>psql</application>, like
> ! this: <literal>echo "\x \\ SELECT * FROM foo;" | psql</literal>.
This should probably use single quotes not double, hm?
regards, tom lane
Tom Lane wrote: > Bruce Momjian <bruce@momjian.us> writes: > > ! pipe the string into <application>psql</application>, like > > ! this: <literal>echo "\x \\ SELECT * FROM foo;" | psql</literal>. > > This should probably use single quotes not double, hm? Yep, done. -- Bruce Momjian bruce@momjian.us EnterpriseDB http://www.enterprisedb.com + If your life is a hard drive, Christ can be your backup. + Index: doc/src/sgml/ref/psql-ref.sgml =================================================================== RCS file: /cvsroot/pgsql/doc/src/sgml/ref/psql-ref.sgml,v retrieving revision 1.177 diff -c -c -r1.177 psql-ref.sgml *** doc/src/sgml/ref/psql-ref.sgml 6 Dec 2006 15:40:11 -0000 1.177 --- doc/src/sgml/ref/psql-ref.sgml 6 Dec 2006 15:46:30 -0000 *************** *** 89,95 **** <acronym>SQL</acronym> and <application>psql</application> meta-commands with this option. To achieve that, you could pipe the string into <application>psql</application>, like ! this: <literal>echo "\x \\ SELECT * FROM foo;" | psql</literal>. (<literal>\\</> is the separator meta-command.) </para> <para> --- 89,95 ---- <acronym>SQL</acronym> and <application>psql</application> meta-commands with this option. To achieve that, you could pipe the string into <application>psql</application>, like ! this: <literal>echo '\x \\ SELECT * FROM foo;' | psql</literal>. (<literal>\\</> is the separator meta-command.) </para> <para>