Universal file access functions provide local access interfaces for files on a database server. Only files in the database cluster directory and the log_directory directory can be accessed. Use a relative path for files in the cluster directory, and a path matching the log_directory configuration setting for log files. Only database system administrators can use these functions.

• pg_ls_dir(dirname text)

  Description: Lists files in a directory.

  Return type: setof text

  Note: pg_ls_dir returns all the names in the specified directory, except the special entries "." and "..".

  For example:

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  SELECT pg_ls_dir('./'); pg_ls_dir ---------------------- .postgresql.conf.swp postgresql.conf pg_tblspc PG_VERSION pg_ident.conf core server.crt pg_serial pg_twophase postgresql.conf.lock pg_stat_tmp pg_notify pg_subtrans pg_ctl.lock pg_xlog pg_clog base pg_snapshots postmaster.opts postmaster.pid server.key.rand server.key.cipher pg_multixact pg_errorinfo server.key pg_hba.conf pg_replslot .pg_hba.conf.swp cacert.pem pg_hba.conf.lock global gaussdb.state (32 rows)

• pg_read_binary_file(filename text [, offset bigint, length bigint,missing_ok boolean])

  Description: Returns the content of a binary file.

  Return type: bytea

  Note: pg_read_binary_file is similar to pg_read_file, except that the result is a bytea value; accordingly, no encoding checks are performed. In combination with the convert_from function, this function can be used to read a file in a specified encoding:

  1	SELECT convert_from(pg_read_binary_file('filename'), 'UTF8');

• pg_stat_file(filename text)

  Description: Returns status information about a file.

  Return type: record

  Note: pg_stat_file returns a record containing the file size, last access timestamp, last modification timestamp, last file status change timestamp, and a Boolean value indicating if it is a directory. Typical use cases are as follows:

  1	SELECT * FROM pg_stat_file('filename');

  1	SELECT (pg_stat_file('filename')).modification;

  For example:

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  SELECT * FROM pg_stat_file('postmaster.pid'); size | access | modification | change | creation | isdir ------+------------------------+------------------------+------------------------ +----------+------- 117 | 2017-06-05 11:06:34+08 | 2017-06-01 17:18:08+08 | 2017-06-01 17:18:08+08 | | f (1 row)

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  SELECT (pg_stat_file('postmaster.pid')).modification; modification ------------------------ 2017-06-01 17:18:08+08 (1 row)