Initial version

.gitignore

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+tmux-collector

config.yml

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+---
+
+# Must match background color of bar or will look weird
+base_bg_color: colour235
+
+# Segments to display (first = left, last = right)
+segments:
+
+  # Arch Linux: Check for Updates
+  - background_success: colour88
+    foreground_success: colour251
+    command: [bash, -c, 'echo "$(checkupdates | wc -l) Updates" | grep -v "^0 Updates" || true']
+    interval: 10m
+
+  # Dropbox CLI: Check daemon status
+  - background_success: colour19
+    foreground_success: colour251
+    command: [bash, -c, 'dropbox.py status | head -n1 | grep -v "Up to date" || true']
+    interval: 30s
+    prefix: ""
+
+  # System: If present display battery status
+  - background_success: colour195
+    foreground_success: colour237
+    command: [tmux-battery]
+
+  # System: Display a stable subset of the uptime
+  - background_success: colour34
+    foreground_success: colour232
+    command: [bash, -c, 'uptime | cut -f 4-5 -d " " | cut -f 1 -d ","']
+
+  # Time
+  - background_success: colour235
+    foreground_success: colour250
+    command: ['date', '+%a, %H:%M:%S']
+
+  # Date
+  - background_success: colour235
+    foreground_success: colour69
+    command: ['date', '+%Y-%m-%d (KW %V)']
+
+...

entry.go

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+package main
+
+import (
+	"crypto/sha256"
+	"encoding/json"
+	"fmt"
+	"os"
+	"path"
+	"strings"
+	"time"
+
+	homedir "github.com/mitchellh/go-homedir"
+)
+
+type config struct {
+	BaseBgColor string     `yaml:"base_bg_color" json:"base_bg_color"`
+	Segments    []*segment `yaml:"segments" json:"segments"`
+}
+
+type segment struct {
+	BackgroundError   string        `yaml:"background_error" json:"background_error"`
+	BackgroundSuccess string        `yaml:"background_success" json:"background_success"`
+	ForegroundError   string        `yaml:"foreground_error" json:"foreground_error"`
+	ForegroundSuccess string        `yaml:"foreground_success" json:"foreground_success"`
+	Command           []string      `yaml:"command" json:"command"`
+	Prefix            string        `yaml:"prefix" json:"prefix"`
+	Interval          time.Duration `yaml:"interval" json:"interval"`
+
+	Output string
+	Err    error
+}
+
+func (s segment) cacheKey() string {
+	return fmt.Sprintf("%x.json", sha256.Sum256([]byte(strings.Join(s.Command, " "))))
+}
+
+func (s segment) storeCache() error {
+	if s.Interval == 0 {
+		// No interval defined = execute all the time, no caching
+		return nil
+	}
+
+	p, err := homedir.Expand(path.Join("~", ".cache", "tmux-collector", s.cacheKey()))
+	if err != nil {
+		return err
+	}
+
+	if err = os.MkdirAll(path.Dir(p), 0700); err != nil {
+		return err
+	}
+
+	fh, err := os.OpenFile(p, os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0600)
+	if err != nil {
+		return err
+	}
+	defer fh.Close()
+
+	return json.NewEncoder(fh).Encode(s)
+}
+
+func (s *segment) loadCache() (bool, error) {
+	if s.Interval == 0 {
+		// No interval defined = execute all the time, no caching
+		return false, nil
+	}
+
+	p, err := homedir.Expand(path.Join("~", ".cache", "tmux-collector", s.cacheKey()))
+	if err != nil {
+		return false, err
+	}
+
+	stat, err := os.Stat(p)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return false, nil
+		}
+		return false, err
+	}
+	if time.Since(stat.ModTime()) > s.Interval {
+		return false, nil
+	}
+
+	fh, err := os.Open(p)
+	if err != nil {
+		return false, err
+	}
+	defer fh.Close()
+
+	if err = json.NewDecoder(fh).Decode(s); err != nil {
+		return false, err
+	}
+
+	return true, nil
+}

main.go

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+package main
+
+import (
+	"bytes"
+	"fmt"
+	"os"
+	"os/exec"
+	"strings"
+	"sync"
+
+	"github.com/Luzifer/rconfig"
+	log "github.com/sirupsen/logrus"
+	yaml "gopkg.in/yaml.v2"
+)
+
+var (
+	cfg = struct {
+		Config         string `flag:"config,c" default:"config.yml" description:"Configuration file"`
+		LogLevel       string `flag:"log-level" default:"info" description:"Log level (debug, info, warn, error, fatal)"`
+		VersionAndExit bool   `flag:"version" default:"false" description:"Prints current version and exits"`
+	}{}
+
+	version = "dev"
+)
+
+func init() {
+	if err := rconfig.ParseAndValidate(&cfg); err != nil {
+		log.Fatalf("Unable to parse commandline options: %s", err)
+	}
+
+	if cfg.VersionAndExit {
+		fmt.Printf("tmux-collector %s\n", version)
+		os.Exit(0)
+	}
+
+	if l, err := log.ParseLevel(cfg.LogLevel); err != nil {
+		log.WithError(err).Fatal("Unable to parse log level")
+	} else {
+		log.SetLevel(l)
+	}
+}
+
+func main() {
+	conf, err := loadConfig()
+	if err != nil {
+		log.WithError(err).Fatal("Unable to load config")
+	}
+
+	wg := &sync.WaitGroup{}
+	wg.Add(len(conf.Segments))
+	for _, seg := range conf.Segments {
+		go executeSegment(seg, wg)
+	}
+	wg.Wait()
+
+	lastBgColor := conf.BaseBgColor
+	output := []string{}
+
+	for _, seg := range conf.Segments {
+		bg := seg.BackgroundSuccess
+		fg := seg.ForegroundSuccess
+
+		if seg.Err != nil {
+			if seg.BackgroundError != "" {
+				bg = seg.BackgroundError
+			}
+			if seg.ForegroundError != "" {
+				fg = seg.ForegroundError
+			}
+
+			if strings.TrimSpace(seg.Output) == "" {
+				seg.Output = seg.Err.Error()
+			}
+		}
+
+		if strings.TrimSpace(seg.Output) == "" {
+			continue
+		}
+
+		if seg.Prefix != "" {
+			seg.Output = strings.Join([]string{seg.Prefix, seg.Output}, " ")
+		}
+
+		if lastBgColor != bg {
+			output = append(output, fmt.Sprintf(" #[fg=%s,bg=%s]#[fg=%s,bg=%s] ",
+				bg, lastBgColor, fg, bg,
+			))
+		} else {
+			output = append(output, fmt.Sprintf("#[fg=%s,bg=%s] ",
+				fg, bg,
+			))
+		}
+		output = append(output, seg.Output)
+		lastBgColor = bg
+	}
+
+	fmt.Print(strings.Join(output, ""))
+}
+
+func executeSegment(seg *segment, wg *sync.WaitGroup) {
+	defer wg.Done()
+
+	loaded, err := seg.loadCache()
+	if err != nil {
+		log.WithError(err).Error("Unable to load cache")
+	}
+	if loaded {
+		log.WithField("command", strings.Join(seg.Command, " ")).Debug("Loaded from cache")
+		return
+	}
+
+	buf := new(bytes.Buffer)
+
+	cmd := exec.Command(seg.Command[0], seg.Command[1:]...)
+	cmd.Stdout = buf
+
+	seg.Err = cmd.Run()
+	seg.Output = strings.Split(buf.String(), "\n")[0]
+	log.WithField("command", strings.Join(seg.Command, " ")).Debug("Freshly loaded")
+
+	if err = seg.storeCache(); err != nil {
+		log.WithError(err).Error("Unable to store cache")
+	}
+}
+
+func loadConfig() (*config, error) {
+	f, err := os.Open(cfg.Config)
+	if err != nil {
+		return nil, err
+	}
+	defer f.Close()
+
+	out := &config{}
+	return out, yaml.NewDecoder(f).Decode(out)
+}