Re: [Help-bash] Use stdin without tempfile

[Peng Yu]

On Sun, Dec 1, 2013 at 5:51 PM, Matthew Cengia <address@hidden> wrote:
> On 2013-12-01 16:59, Peng Yu wrote:
>> Hi,
>>
>> I want to process stdin in the way that the first 10 lines are
>> processed by prog1, and the remaining lines are processed by prog2.
>>
>> The output of prog1 is printed to stdout first, then the output of
>> prog2 is printed to stdout. No tempfiles should be created, but fifo
>> can be created. Is it possible?
>>
>> When the input is not stdin, a script like the following can be easily
>> created. But when the input is a pipe, it is not clear to me what to
>> do without creating a tempfile.
>
> bash$ printf "%s\n" {1..30} > file.txt
> bash$ cat main.sh
> #!/bin/bash
>
> prog1(){
>   local line
>   while read -r line
>   do
>     printf "PROG1: %s\n" "$line"
>   done
> }
> prog2(){
>   local line
>   while read -r line
>   do
>     printf "PROG2: %s\n" "$line"
>   done
> }
>
> {
>   for i in {1..10}
>   do read -r line
>     echo "$line"
>   done | prog1
>
>   prog2
> } < "$1"

10 is just an example. When 10 becomes a very large number or the
input is very long, I guess this is not very efficient? Is there a
more efficient solution?

> bash$ ./main.sh file.txt
> PROG1: 1
> PROG1: 2
> PROG1: 3
> PROG1: 4
> PROG1: 5
> PROG1: 6
> PROG1: 7
> PROG1: 8
> PROG1: 9
> PROG1: 10
> PROG2: 11
> PROG2: 12
> PROG2: 13
> PROG2: 14
> PROG2: 15
> PROG2: 16
> PROG2: 17
> PROG2: 18
> PROG2: 19
> PROG2: 20
> PROG2: 21
> PROG2: 22
> PROG2: 23
> PROG2: 24
> PROG2: 25
> PROG2: 26
> PROG2: 27
> PROG2: 28
> PROG2: 29
> PROG2: 30
>
> --
> Regards,
> Matthew Cengia



-- 
Regards,
Peng