Golang : Skip or discard items of non-interest when iterating example


Tags : golang read-file skip-iterable-item strings-index

Problem:

You want to skip or discard items of non-interest when iterating. For example, skipping the commented lines with # sign in the /etc/passwd file.

 ##
 # User Database
 #
 # Note that this file is consulted directly only when the system is running
 # in single-user mode.  At other times this information is provided by
 # Open Directory.
 #
 # See the opendirectoryd(8) man page for additional information about
 # Open Directory.
 ##
 nobody:*:-2:-2:Unprivileged User:/var/empty:/usr/bin/false
 root:*:0:0:System Administrator:/var/root:/bin/sh
 daemon:*:1:1:System Services:/var/root:/usr/bin/false

Solution:

Test each line(item) with strings.Index() function to see if the line starts with # sign. If the # sign is detected, skip or discard the item. This example reads the iterable items from a file; however, you can easily modify it to accommodates array or slice.

 package main

 import (
 "bufio"
 "fmt"
 "io"
 "os"
 "strings"
 )

 func main() {
 file, err := os.Open("/etc/passwd")

 if err != nil {
 fmt.Println(err)
 os.Exit(1)
 }

 defer file.Close()

 reader := bufio.NewReader(file)

 for {
 line, err := reader.ReadString('\n')

 // skip all line starting with #
 if equal := strings.Index(line, "#"); equal < 0 {
 fmt.Print(line)
 }

 // alternatively, only print line starting with #
 //if equal := strings.Index(line, "#"); equal >= 0 {
 // fmt.Print(line)
 // }

 if err == io.EOF {
 break
 }
 if err != nil {
 fmt.Println(err)
 os.Exit(1)
 }

 }

 }

Output:

 nobody:*:-2:-2:Unprivileged User:/var/empty:/usr/bin/false
 root:*:0:0:System Administrator:/var/root:/bin/sh
 daemon:*:1:1:System Services:/var/root:/usr/bin/false

References:

https://www.socketloop.com/tutorials/golang-read-data-from-config-file-and-assign-to-variables

https://golang.org/pkg/strings/#Index

  See also : Golang : Read data from config file and assign to variables



Tags : golang read-file skip-iterable-item strings-index

By Adam Ng

IF you gain some knowledge or the information here solved your programming problem. Please consider donating to the less fortunate or some charities that you like. Apart from donation, planting trees, volunteering or reducing your carbon footprint will be great too.


Advertisement