Pg gethostname
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Revision as of 09:03, 25 February 2013 by Yin_yang2k (Talk | contribs)
C function to get server hostname
Works with PostgreSQL
9.0+
Written in
C
Depends on
Nothing
Here is a compilable C function to get the server hostname.
Tested with CentOS 5 x86_64, postgresql 9.0 & 9.1.
Probably works in earlier versions of pg and other linux distros, but haven't tested.
/* A PostgreSQL function for getting the hostname. File: `pg_config --libdir`/pg_gethostname.c To compile... (make sure pg_config is in your PATH) gcc -I$(pg_config --includedir-server) -fpic -c pg_gethostname.c -L$(pg_config --libdir) gcc --shared -o pg_gethostname.so pg_gethostname.o To create the funciton in PostgreSQL... CREATE OR REPLACE FUNCTION pg_gethostname() RETURNS text AS 'pg_gethostname' LANGUAGE C IMMUTABLE STRICT; */ #include "postgres.h" #include <limits.h> #include <unistd.h> #include <string.h> #include "fmgr.h" #include "utils/palloc.h" #include "utils/elog.h" #include "storage/bufpage.h" #ifdef PG_MODULE_MAGIC PG_MODULE_MAGIC; #endif PG_FUNCTION_INFO_V1( pg_gethostname ); Datum pg_gethostname( PG_FUNCTION_ARGS ); Datum pg_gethostname( PG_FUNCTION_ARGS ) { text *t; char server_hostname[HOST_NAME_MAX]; size_t length; if ( gethostname( server_hostname, HOST_NAME_MAX ) != 0 ) { // returning an empty string for the hostname if it fails makes // sense because if it succeeded, we would have a name server_hostname[0] = '\0'; } length = strnlen( server_hostname, HOST_NAME_MAX ); t = (text *) palloc(VARHDRSZ + length ); SET_VARSIZE( t, VARHDRSZ + length ); memcpy( VARDATA(t), server_hostname, length ); PG_RETURN_TEXT_P( t ); }
Usage:
postgres# select pg_gethostname(); pg_gethostname ---------------- myserver
Installation with a makefile
http://www.postgresql.org/docs/9.1/static/extend-pgxs.html
This worked for me on Ubuntu 12.04 64bit PostgreSQL 9.1
Create a makefile in the directory of your choice
# makefile MODULES = pg_gethostname PG_CONFIG = pg_config PGXS := $(shell $(PG_CONFIG) --pgxs) include $(PGXS)
Put pg_gethostname.c in the same directory and run the following script. You have to have pg_config in your path
#!/bin/bash # Install script PGXS=`pg_config --pgxs` PG_CONFIG=`which pg_config` make make install echo "CREATE OR REPLACE FUNCTION pg_gethostname() RETURNS text AS 'pg_gethostname' LANGUAGE C IMMUTABLE STRICT;" | psql -U postgres template1
