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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. ...

Recently I have been in a situation where I needed a simple ‘batch’ job scheduler, where I could submit some long-running tasks to a server and have a ‘system’ that serialize access the execution with some basic job control facilities (remove a job from the queue, stop the processing, and so on). Linux printing subsystem is already designed to do this, and we can exploit the CUPS printing subsystem to run our “batch” jobs. ...

Pubblico qui le slide che ho usato durante la serata dedicata alla programmazione Python, svoltasi presso il FabLab Verona http://ilmanzo.github.io/files/slide_serata_python_fablab_2015.html

Following with the GO standard library exploration, I’ve written a toy example for using the CGI features. Native GoLang CGI web applications are very fast and can be useful for example in embedded systems, or in cheap web hosting where is not possible to run custom HTTP servers. The solution has some weak points, starting from lock management, but is only presented as a proof of concept and not for real use cases. ...