💾 Intro I just found a very cheap SD card on an online store and since I know that there are some fake around, I wanted to quickly test if its size and speed respect the specs. Edit: after first publish, a kind reader noticed me that The F3 tools are a perfect fit for the same task and that’s right; if you want to follow a manual path and learn something in the journey, continue reading… ...
I have a binary file with data stored as two-byte big-endian 16-bit words. We need to extract the values in the file and print them in decimal ASCII format, so to obtain numbers in the 0-655535 range. let’s create the sample file: $ echo -en "\x01\x02\x03\x04\x05\x06\x07\x08" > file.bin and show its content in binary form: $ hexdump -C file.bin 00000000 01 02 03 04 05 06 07 08 |........| 00000008 to get the desired output we can use the powerful, but little documented format string option of hexdump: ...
I want to keep under control a system where each user has an amount of filesystem quota reserved; in particular I would like to get notified if and when a user exceeds some treshold. Since I already have Monit in place in the server, I took the chance to write a small Go utility in order to retrieve the quota percentage. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 // quotachecker.go package main import ( "os" "os/exec" "regexp" "strconv" "strings" ) func main() { //a fake implementation, just for testing purpose //cmd := exec.Command("/bin/sh", "-c", "cat fakequota.txt") cmd := exec.Command("/usr/bin/repquota", "-a") stdout, err := cmd.Output() if err != nil { panic(err.Error()) } re, err := regexp.Compile("^[[:alnum:]]+\\s+--\\s+\\d+\\s+\\d+") if err != nil { panic(err.Error()) } percent_max := 0 result := strings.Split(string(stdout), "\n") for _, line := range result { match := re.MatchString(line) if !match { continue } fields := strings.Fields(line) spaceused, err := strconv.ParseInt(fields[2], 10, 64) if err != nil { panic(err.Error()) } spacetotal, err := strconv.ParseInt(fields[4], 10, 64) if err != nil { panic(err.Error()) } if spacetotal == 0 { continue } //calculate max percent used percent := int(100 * spaceused / spacetotal) if percent > percent_max { percent_max = int(percent) } } os.Exit(percent_max) } This is also an example on how to run external programs in Go and filter the output using regular expressions. ...
Obiettivo vogliamo mantenere la stessa directory sincronizzata su due server linux. Questo significa che ogni aggiunta/rimozione/modifica di file in questa directory verrà automaticamente riportato sull’altro (salvo conflitti). Diamo per assunto che i due server siano raggiungibili via rete, ma per qualsiasi motivo non sia possibile collegare dello spazio disco condiviso. Implementazione Per raggiungere lo scopo, utilizzeremo il tool: csync2 su entrambi i server (che chiameremo nodo1 e nodo2), installiamo i pacchetti necessari: ...