pgconf

pgconf is a simple Go package for reading/writing to PostgreSQL config file (postgresql.conf) that:

• Preseves existing whitespace and comments
• Supports single quoted and backslash-quoted values (eg. search_path = '''$user'', \'public\'')
• Supports values with optional equal sign (eg. logconnections yes)
• Works with ASCII and UTF-8 .conf files

How to use

postgresql.conf:

To read or update postgresql.conf files use the pgconf/conf package:

import (
    "fmt"
    "github.com/quasoft/pgconf/conf"
)
func main() {
    c, err := conf.Open("/data/postgresql.conf")
    if err != nil {
        panic("Could not open conf file: " + err.Error())
    }
    // StringK automatically dequotes values
    dest, err := c.StringK("log_destination")
    if err != nil || dest != "syslog" {
        // If key was not set or has the wrong value
        fmt.Println("log_destination value is not what we want, changing it now")
        c.SetStringK("log_destination", "syslog") // SetStringK automatically quotes values if necessary
    }
    err = c.WriteFile("/data/postgresql.conf", 0644)
    if err != nil {
        panic("Could not save file: " + err.Error())
    }
}

pg_hba.conf

To read or update pg_hba.conf files use the pgconf/hba package:

package main
import (
    "fmt"
    "github.com/quasoft/pgconf/hba"
)
func main() {
    conf, err := hba.Open("../../hba/testdata/sample.conf") // pg_hba.conf
    if err != nil {
        panic(fmt.Errorf("Failed opening file pg_hba.conf: %s", err))
    }
    // Find all rows for replication host-based authentication
    rows, err := conf.LookupAll(hba.Database, "replication")
    if err != nil {
        panic(fmt.Errorf("Failed looking up for replication rows: %s", err))
    }
    fmt.Printf("Found %d replication rows with addresses as follows:\n", len(rows))
    for _, row := range rows {
        // Get and print value for ADDRESS column
        address, err := conf.String(row, hba.Address)
        if err != nil {
            panic(fmt.Errorf("Could not read address value: %s", err))
        }
        fmt.Println(" - " + address)
    }
}

outputs:

Found 3 replication rows with addresses as follows:
 - 127.0.0.1/32
 - ::1/128
 - 10.0.0.3/32

Hint

Usually it’s safer to write changes to a temp file and once that writing is over to rename
the temp file to the actual configuration file:

    ...
    err = c.WriteFile("/data/postgresql.conf.tmp", 0644)
    if err != nil {
        panic("Could not save file: " + err.Error())
    }
    err = os.Rename("/data/postgresql.conf.tmp", "/data/postgresql.conf")
    if err != nil {
        panic("Could not rename tmp file to conf: " + err.Error())
    }
    ...
}

If you use this approach make sure to store the temp file in a secure location (eg. the data
dir) with restricted permissions and not inside the /tmp directory.