Re: Read a fixed length of input each time

[Peng Yu]

It is to deal with binary files. For example, I may create a binary
stream using the following Go file.

```
// main.go
package main

import (
  "bufio"
  "strconv"
  "encoding/binary"
  "io"
  "os"
  "log"
)

func main() {
  stdin := bufio.NewReader(os.Stdin)
  for {
    line, err := stdin.ReadBytes('\n')
    if err == io.EOF {
      if len(line) == 0 { break }
    } else {
      if err != nil { log.Fatal(err) }
      line = line[:(len(line)-1)]
    }
    x, err := strconv.ParseUint(string(line), 0, 32)
    if err != nil { log.Fatal(err) }
    err = binary.Write(os.Stdout, binary.LittleEndian, uint32(x))
    if err != nil { log.Fatal(err) }
  }
}
```

Then I may need to deal with the binary output of main.go.

$ seq 10 | go run main.go | xxd
00000000: 0100 0000 0200 0000 0300 0000 0400 0000  ................
00000010: 0500 0000 0600 0000 0700 0000 0800 0000  ................
00000020: 0900 0000 0a00 0000                      ........


On 6/23/20, Andrew J. Schorr <aschorr@telemetry-investments.com> wrote:
> On Tue, Jun 23, 2020 at 09:53:57AM -0500, Neil R. Ormos wrote:
>>   RS="................"
> ...
>> Then, each getline will place chunk-size characters in RT, provided there
>> are enough characters available to match RS.  Otherwise, the residual
>> characters on the final getline resulting in reaching the end-of-file will
>> be placed in the variable specified to receive the results from getline.
>
> That's a creative solution to the problem.
>
>> [*1] I acknowledge the warnings from the developers and their suggestions
>> that reading binary data can best be done with an extension or some
>> pre-processing step.  But those solutions may not be available or uniform
>> in all environments where gawk is available.  So, even if this RS-based
>> method is not as good, it might allow the user to write a relatively
>> portable program intended for several heterogeneous environments.
>
> I'll bite -- what's the benefit of reading binary data like this? What do
> you
> do with it once you get it inside gawk? It's easy enough to add read and
> write
> functions in an extension library, but I've never understood the usage
> case.
> It would take maybe 15 minutes to add these functions to the select
> extension,
> but I need a reason. And yes, as you point out, an extension is an
> additional
> installation dependency.
>
> Regards,
> Andy
>
>


-- 
Regards,
Peng