File: gobble.go
   1 /*
   2 The MIT License (MIT)
   3 
   4 Copyright © 2020-2025 pacman64
   5 
   6 Permission is hereby granted, free of charge, to any person obtaining a copy of
   7 this software and associated documentation files (the “Software”), to deal
   8 in the Software without restriction, including without limitation the rights to
   9 use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
  10 of the Software, and to permit persons to whom the Software is furnished to do
  11 so, subject to the following conditions:
  12 
  13 The above copyright notice and this permission notice shall be included in all
  14 copies or substantial portions of the Software.
  15 
  16 THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  17 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  18 FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  19 AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  20 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  21 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  22 SOFTWARE.
  23 */
  24 
  25 /*
  26 Single-file source-code for gobble.
  27 
  28 To compile a smaller-sized command-line app, you can use the `go` command as
  29 follows:
  30 
  31 go build -ldflags "-s -w" -trimpath gobble.go
  32 */
  33 
  34 package main
  35 
  36 import (
  37     "bytes"
  38     "io"
  39     "os"
  40     "os/exec"
  41 )
  42 
  43 const info = `
  44 gobble [command...] [args...]
  45 
  46 Read all bytes from standard input, and only then emit them out, or run
  47 the command given, sending those bytes to its standard input.
  48 `
  49 
  50 func main() {
  51     if len(os.Args) > 1 {
  52         switch os.Args[1] {
  53         case `-h`, `--h`, `-help`, `--help`:
  54             os.Stderr.WriteString(info[1:])
  55             return
  56         }
  57     }
  58 
  59     // wait until the last byte is read
  60     input, err := io.ReadAll(os.Stdin)
  61     if err != nil {
  62         showError(err)
  63         os.Exit(1)
  64     }
  65 
  66     // emit data just read and quit, if no command was given
  67     if len(os.Args) == 1 {
  68         os.Stdout.Write(input)
  69         return
  70     }
  71 
  72     // run a command, using the data just read for its stdin
  73     name := os.Args[1]
  74     args := os.Args[2:]
  75     cmd := exec.Command(name, args...)
  76     cmd.Stdin = bytes.NewReader(input)
  77     cmd.Stdout = os.Stdout
  78     cmd.Stderr = os.Stderr
  79 
  80     if err := cmd.Start(); err != nil {
  81         showError(err)
  82     }
  83 
  84     if err := cmd.Wait(); err != nil {
  85         showError(err)
  86     }
  87 
  88     os.Exit(cmd.ProcessState.ExitCode())
  89 }
  90 
  91 // showError gives a consistent style/look to any of the app's own errors
  92 func showError(err error) {
  93     os.Stderr.WriteString("\x1b[31m")
  94     os.Stderr.WriteString(err.Error())
  95     os.Stderr.WriteString("\x1b[0m\n")
  96 }