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Editing: pg_wrapper

#!/usr/bin/perl
# Call a PostgreSQL client program with the version, cluster and default
# database specified in ~/.postgresqlrc or
# /etc/postgresql-common/user_clusters.
#
# (C) 2005-2009 Martin Pitt <mpitt@debian.org>
# (C) 2013-2021 Christoph Berg <myon@debian.org>
#
#  This program is free software; you can redistribute it and/or modify
#  it under the terms of the GNU General Public License as published by
#  the Free Software Foundation; either version 2 of the License, or
#  (at your option) any later version.
#
#  This program is distributed in the hope that it will be useful,
#  but WITHOUT ANY WARRANTY; without even the implied warranty of
#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#  GNU General Public License for more details.

use warnings;
use strict;
use POSIX;
use PgCommon;

my ($version, $cluster);
my $explicit_host = exists $ENV{PGHOST};
my $explicit_port = exists $ENV{PGPORT};
my $explicit_service = exists $ENV{PGSERVICE};

# Evaluate PGCLUSTER (unless PGHOST is set as well)
if (exists $ENV{'PGCLUSTER'} and not $explicit_host) {
    ($version, $cluster) = split ('/', $ENV{'PGCLUSTER'}, 2);
    error "Invalid version $version specified in PGCLUSTER" unless version_exists $version;
    error 'No cluster specified with $PGCLUSTER' unless $cluster;
}

# Check for --cluster argument and filter it out
for (my $i = 0; $i <= $#ARGV; ++$i) {
    last if $ARGV[$i] eq '--';

if ($ARGV[$i] eq '--cluster') {
        error '--cluster option needs an argument (<version>/<cluster>)' if ($i >= $#ARGV);

($version, $cluster) = split ('/', $ARGV[$i+1], 2);
        error "Invalid version $version specified with --cluster" unless version_exists $version;
        error 'No cluster specified with --cluster' unless $cluster;

splice @ARGV, $i, 2;
        last;
    } elsif ($ARGV[$i] =~ /^--cluster=(\d+\.?\d)\/(.+)/) {
        ($version, $cluster) = ($1, $2);
        error "Invalid version $version specified with --cluster" unless version_exists $version;
        error 'No cluster specified with --cluster' unless $cluster;

splice @ARGV, $i, 1;
        last;
    }
    # --host or -h on command line, drop info from PGCLUSTER
    if ($ARGV[$i] =~ /^--host\b/ || $ARGV[$i] =~ /^-\w*h\w*$/) {
        ($version, $cluster) = (undef, undef);
        $explicit_host = 1;
        delete $ENV{PGCLUSTER};
    }
    # --port or -p on command line
    if ($ARGV[$i] =~ /^--port\b/ || $ARGV[$i] =~ /^-\w*p\w*$/) {
        $explicit_port = 1;
    }
    # "service=" in connection string
    if ($ARGV[$i] =~ /\bservice=/) {
        $explicit_service = 1;
    }
}

my ($db);

# if we don't have a cluster, and no specific host was given, consult postgresqlrc
# or fall back to default port cluster (on 5432), or undef otherwise
($version, $cluster, $db) = user_cluster_map() unless ($cluster or $explicit_host);

my ($host, $port);

if ($cluster) {
    # check if we have a network cluster (N.N/the.host.name:port)
    if ($cluster =~ /^(\S+):(\d*)$/) {
	$host = $1;
	$port = $2 || $PgCommon::defaultport;
    } elsif (not cluster_exists($version, $cluster)) {
        # a specific cluster was requested, error out because it doesn't exist
        error "Cluster $version $cluster does not exist";
    } else {
        $host = get_cluster_socketdir ($version, $cluster);
        $port = get_cluster_port($version, $cluster);
    }
    # set PGCLUSTER variable for information
    $ENV{PGCLUSTER} = "$version/$cluster";
}

# setup environment
$ENV{'PGSYSCONFDIR'} //= '/etc/postgresql-common';
$ENV{'PGHOST'} = $host if ($host);
$ENV{'PGPORT'} = $port if $port && !$ENV{'PGPORT'};
$ENV{'PGDATABASE'} = $db if $db && !$ENV{'PGDATABASE'};

# check under which name we were called
my $cmdname = (split '/', $0)[-1];

unless ($version or $explicit_host or $explicit_port or $explicit_service) {
    print STDERR "Warning: No existing cluster is suitable as a default target. Please see man pg_wrapper(1) how to specify one.\n";
}

# if we have no version yet, use the latest version. If we were called as psql,
# pg_archivecleanup, or pg_isready, always use latest version
if (not $version or $cmdname =~ /^(psql|pg_archivecleanup|pg_isready)$/) {
    $version = get_newest_version($cmdname);
}
unless ($version) {
    error 'You must install at least one postgresql-client-<version> package';
}
error "PostgreSQL version $version is not installed" unless -d "$PgCommon::binroot$version";

my $cmd;
if ($cmdname eq 'pg_wrapper') {
    error "pg_wrapper called directly but no program given as argument"
        if (@ARGV == 0);
    $cmd = shift; # will be unshifted back below
} else {
    $cmd = get_program_path ($cmdname, $version);
}

# libreadline is a lot better than libedit, so prefer that on versions that still use it
if ($cmdname eq 'psql' and $version < 13 and not $PgCommon::rpm) {
    my @readlines;
    # non-multiarch path
    @readlines = sort(</lib/libreadline.so.?>);

unless (@readlines) {
	# get multiarch dir for our architecture
	if (open PS, '-|', '/usr/bin/ldd', $cmd) {
	    my $out;
	    read PS, $out, 10000;
	    close PS;
	    if ($out =~ m!/libreadline.so!) {
		# already linked against libreadline
		@readlines = ();
	    }
	    else
	    {
		my ($lib_path) = $out =~ m!(/lib/.*)/libedit.so!;

@readlines = sort(<$lib_path/libreadline.so.?>);
	    }
	}
    }

if (@readlines) {
	$ENV{'LD_PRELOAD'} = ($ENV{'LD_PRELOAD'} or '') . ':' . $readlines[-1];
    }
}

error "pg_wrapper: $cmdname was not found in $PgCommon::binroot$version/bin" unless $cmd;
unshift @ARGV, $cmd;
exec @ARGV;

__END__

=head1 NAME

pg_wrapper - wrapper for PostgreSQL client commands

=head1 SYNOPSIS

I<client-program> [B<--cluster> I<version>/I<cluster>] [...]

(I<client-program>: B<psql>, B<createdb>, B<dropuser>, and all other client
programs installed in C</usr/lib/postgresql/>I<version>C</bin>).

=head1 DESCRIPTION

This program is run only as a link to names which correspond to PostgreSQL
programs in C</usr/lib/postgresql/>I<version>C</bin>. It determines the
configured cluster and database for the user and calls the appropriate version
of the desired program to connect to that cluster and database, supplying any
specified options to that command.

The target cluster is selected by the following means, in descending order of
precedence:

=over

=item 1.

explicit specification with the B<--host> option

=item 2.

explicit specification with the B<--cluster> option

=item 3.

if the B<PGHOST> environment variable is set, no further cluster selection is
performed. The default PostgreSQL version and port number (from the command
line, the environment variable B<PGPORT>, or default 5432) will be used.

=item 4.

explicit specification with the B<PGCLUSTER> environment variable

=item 5.

matching entry in C<~/.postgresqlrc> (see L<postgresqlrc(5)>), if that
file exists

=item 6.

matching entry in C</etc/postgresql-common/user_clusters> (see
L<user_clusters(5)>), if that file exists

=item 7.

If only one cluster exists on the local system, that one will be selected.

=item 8.

If several clusters exist on the local system, the one listening on the default port 5432
will be selected.

=back

If none of these rules match, B<pg_wrapper> does not set any environment
variables and the program called will likely error out with a message like
"could not connect to server: Connection refused".

For B<psql>, B<pg_archivecleanup>, and B<pg_isready>, B<pg_wrapper> will always use the binary from
the newest PostgreSQL version installed, as these are downwards compatible.

Note that B<pg_wrapper> needs to be able to read the server config to get the
port number to connect to. If a non-standard port is configured in a place that
pg_wrapper cannot read, connecting will fail. This particularly holds if the
port was configured via B<ALTER SYSTEM> in C<postgresql.auto.conf> and
pg_wrapper is invoked as any user other than B<postgres> and B<root>.

=head1 OPTIONS

=over

=item B<--cluster> I<version>B</>I<cluster>

=item B<--cluster> I<version>B</>I<host>B<:>[I<port>]

I<cluster> is either the name of a cluster on the local system, or takes the form
I<host>:I<port> for a remote cluster. If I<port> is left empty (i. e. you just
specify I<host:>), it defaults to 5432.

=back

=head1 ENVIRONMENT

=over

=item B<PGCLUSTER>

If C<$PGCLUSTER> is set, its value (of the form I<version>/I<cluster>)
specifies the desired cluster, similar to the B<--cluster> option. However, if
B<--cluster> is specified, it overrides the value of C<$PGCLUSTER>.

=item B<PG_CLUSTER_CONF_ROOT>

This specifies an alternative base directory for cluster configurations. This
is usually C</etc/postgresql/>, but for testing/development purposes you can
change this to point to e. g. your home directory, so that you can use the
postgresql-common tools without root privileges.

=item B<PGSYSCONFDIR>

This is the location of PostgreSQL's and postgresql-common's global
configuration (e. g. C<pg_service.conf>, L<user_clusters(5)>). The default is
C</etc/postgresql-common/>.

=back

=head1 FILES

=over

=item C</etc/postgresql-common/user_clusters>

stores the default cluster and database for users and groups as set by
the administrators.

=item C<$HOME/.postgresqlrc>

stores defaults set by the user himself.

=back

=head1 SEE ALSO

L<user_clusters(5)>, L<postgresqlrc(5)>

=head1 AUTHOR

Martin Pitt L<E<lt>mpitt@debian.orgE<gt>>

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