Hi,
In unix a process has stdin (normally keyboard), stdout (echo in a
script etc) and stderr (error messages) by default. However, you can
override this and the process won't know.
echo 'abcd' > test.txt
tells the shell to let the output of the program echo go to file
test.txt instead of the screen (ie redirect of stdout). For stderr
different shells have different syntax. The 2> thing has to do with
this. In the example below you tell stderr to go where stdout goes
(~/logfile).
If you do
psql database < data.sql
...the shell uses file data.sql as stdin instead of "the keyboard". That
is, the content of data.sql is treated as if you would have been typing
it by hand.
cat data.sql | psql database
...would do the same thing as pipe connects stdout of the program to the
left to stdin of the program to the right.
The error message indicates that there is no file data.sql in the
current directory.
Hope this helps,
Marcus
john hedge wrote:
> Hi,
>
> As you'll realise I'm new to all things Postgresql (& Gambas) and e-mail
> lists.
>
> I'm following Dr Bain's article in LXF71.
>
> Everything has gone ok (now) up until the introduction of "< data.sql"
> as per below.
>
> Can someone explain what we're trying to do here, and more importantly
> why it's not working and what I've done wrong, please?
>
> TIA
>
> John
>
> postgres@zaphod2:~$ /usr/lib/postgresql/bin/initdb
> -D /usr/local/pgsql/data/
> The files belonging to this database system will be owned by user
> "postgres".
> This user must also own the server process.
>
> The database cluster will be initialized with locale C.
>
> initdb: directory "/usr/local/pgsql/data/" exists but is not empty
> If you want to create a new database system, either remove or empty
> the directory "/usr/local/pgsql/data/" or run initdb with an argument
> other than
> "/usr/local/pgsql/data/".
> postgres@zaphod2:~$ /usr/lib/postgresql/bin
> /postmaster
> -D /usr/local/pgsql/data/ >~/logfile 2>&1 &
> [1] 14081
> postgres@zaphod2:~$ /usr/lib/postgresql/bin/createdb customers CREATE
> DATABASE
> [1]+ Exit 1 /usr/lib/postgresql/bin/postmaster
> -D /usr/local/pgsql/data/ >~/logfile 2>&1
> postgres@zaphod2:~$ /usr/lib/postgresql/bin/psql customers < data.sql
> bash: data.sql: No such file or directory
