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waitfor

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[![Go Report Card](https://goreportcard.com/badge/github.com/Luzifer/waitfor)](https://goreportcard.com/report/github.com/Luzifer/waitfor)
![](https://badges.fyi/github/license/Luzifer/waitfor)
![](https://badges.fyi/github/downloads/Luzifer/waitfor)
![](https://badges.fyi/github/latest-release/Luzifer/waitfor)
# Luzifer / waitfor
`waitfor` is a small utility to check the exit code of an command to be used within a shell command.
## Usage
```console
$ waitfor --help
Usage of waitfor:
-i, --check-interval duration How long to wait after an unsuccessful check (default 1s)
-c, --command-timeout duration Stop the command execution after this time
--log-level string Log level (debug, info, warn, error, fatal) (default "info")
-s, --shell string Shell to execute with the given command (must accept -c flag) (default "/bin/bash")
--version Prints current version and exits
-w, --wait-timeout duration Stop waiting for the command after this time
```
When a `wait-timeout` is specified and the check command did not exit with status code 0 before the timeout is reached `waitfor` will exit with status 1. This ensures a shell command connected with `&&` is not executed afterwards.
## Examples
- Wait for the VPN connection to be available before executing a command using it
```console
$ waitfor 'ip a | grep 10.123.0' && echo "VPN connected"
```
- Ensure you are online before executing a curl command
```console
$ waitfor -- ping -c 1 8.8.8.8 && curl ...
```
- Wait at most 5m for a file to appear before accessing it
```console
$ waitfor -w 5m -- ls myfile && cat myfile
```

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package main
import (
"context"
"fmt"
"os"
"os/exec"
"strings"
"time"
"github.com/pkg/errors"
log "github.com/sirupsen/logrus"
"github.com/Luzifer/rconfig"
)
var (
cfg = struct {
CheckInterval time.Duration `flag:"check-interval,i" default:"1s" description:"How long to wait after an unsuccessful check"`
CommandTimeout time.Duration `flag:"command-timeout,c" default:"0" description:"Stop the command execution after this time"`
LogLevel string `flag:"log-level" default:"info" description:"Log level (debug, info, warn, error, fatal)"`
Shell string `flag:"shell,s" default:"/bin/bash" description:"Shell to execute with the given command (must accept -c flag)"`
WaitTimeout time.Duration `flag:"wait-timeout,w" default:"0" description:"Stop waiting for the command after this time"`
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("waitfor %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() {
started := time.Now()
for {
if err := executeCommand(rconfig.Args()[1:]); err == nil {
break
} else {
log.WithField("error", err.Error()).Debug("Command was not successful")
}
if cfg.WaitTimeout > 0 && started.Add(cfg.WaitTimeout).Before(time.Now()) {
log.WithField("timeout", cfg.WaitTimeout).Fatal("Wait timed out")
}
time.Sleep(cfg.CheckInterval)
}
log.Info("Command exited successful")
}
func executeCommand(cmdStr []string) error {
cmd := exec.Command(cfg.Shell, "-c", strings.Join(cmdStr, " "))
var (
c = make(chan error, 1)
ctx = context.Background()
cancel context.CancelFunc = func() {}
)
if cfg.CommandTimeout > 0 {
ctx, cancel = context.WithTimeout(context.Background(), cfg.CommandTimeout)
}
go func() {
c <- cmd.Run()
}()
for {
select {
case <-ctx.Done():
cmd.Process.Kill()
return errors.New("Command execution timed out")
case err := <-c:
cancel()
return err
}
}
}