Golang : Skip or discard items of non-interest when iterating example
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
See also : Golang : Read data from config file and assign to variables
By Adam Ng
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