about batch command, pipe

[edisonx]

hello, everyone,

I wonder to know , how to using redirection pipe ( | ),

so I write three batch files (sum.bat, rstring3.bat main.bat) to test.

like those

:: filename : sum.bat
@echo off
:main
  SET low=%~1%
  SET  up=%~2%
  SET ret=0
  FOR /L %%I IN (%low%,1,%up%) DO (
    SET /A ret+=%%I
  )
  echo %low%+...+%up%=%ret%

:: filename : rstring3.bat

@echo off
:main
  SET String=%1%
  SET String=%String:~-3%
  echo %String%

:: filename : main.bat
  rstring3.bat | sum.bat 1 10

in command line, I type

C:\>  main.bat

It wilil display 1+...+10=55

but I think it will display 55

what's wrong with the code ?

how can I do to fix the wrong answer ?

thanks for everyone, and sorry for my poor English.

[allen2]

The "|" is used the same way as other OS use it and the command placed at the right of the pipe will process the result of the command placed before.

As for your example, i don't understand what you're trying to do so i can really help there but the only way it would make sense would be :

main.bat

sum.bat 1 10| rstring3.bat 

and modify also

rstring.bat

@echo off
:main
  SET String=%ret%
  SET String=%String:~-3%
  echo %String%

More info about pipe there and the full history there.

Edit reason: forgot to say that the output of a batch can't be considered as the argument of another and then you have to pass through another way like a variable.

Edited September 15, 2011 by allen2

[edisonx]

thanks for your replay, allen2 .

I had studying the website that you gave to me.

I really misunderstood pipe '|' ,

thank you a again.

I used to programming in C/C++ language,

but learning to use batch command recently by some reasons.

I think that there are many instructions in *.h files in C,

so what I need , call the instruction just include ???.h file.

But in batch, if there is a batch command was used frequently,

will it be written down again in different batch files ? just like sum.bat

I had ever try this code

@echo off

:main
SET rst=0
call :sum 1 10 rst
echo %rst%
goto :eof 

:: --------------------------------
:: param 0 : sum (function name)
:: param 1 : low bound
:: param 2 : up bound
:: param 3 : ans
:: --------------------------------
:sum
SETLOCAL ENABLEDELAYEDEXPANSION &Rem using local variable
  SET low=%~1%
  SET  up=%~2%
  SET rst=0
  FOR /L %%i IN (%low%,1,%up%) DO (
    SET /A rst+=%%i
  )
(ENDLOCAL &Rem return value
  SET %3=%rst%
)
goto :eof  

in this case,if sum function is used frequently, I think that coding it in another .bat is better , right ?

I'm confused how to like C language, to make a function-like batch,

let other batch files can re-used.

Is this the only way to maintain the source ?

:: filename : sum.bat

:: --------------------------------
:: param 0 : sum (function name)
:: param 1 : low bound
:: param 2 : up bound
:: param 3 : ans
:: --------------------------------
:sum
SETLOCAL ENABLEDELAYEDEXPANSION &Rem using local variable
  SET low=%~1%
  SET  up=%~2%
  SET rst=0
  FOR /L %%i IN (%low%,1,%up%) DO (
    SET /A rst+=%%i
  )
(ENDLOCAL &Rem return value
  SET %3=%rst%
)
goto :eof  

:: filename : demo_sum.bat
@echo off
:demo_sum
  SET ret=0
  call sum.bat 1 10 ret
  echo ret=%ret%

your reply helps me a lot!!

thank you again *^_^*

[jaclaz]

Edit reason: forgot to say that the output of a batch can't be considered as the argument of another and then you have to pass through another way like a variable.

Not really-really.

There are tricks :

http://www.robvanderwoude.com/files/readline_2k.txt

essentially:

::pipetome.cmd
::A batch capable of accepting PIPE input
@ECHO OFF
SETLOCAL ENABLEEXTENSIONS
FOR /F "tokens=*" %%A IN ('MORE') DO SET Got_From_Pipe=%%A
SET Got_From_Pipe

jaclaz

[allen2]

It was clear to me that you were more used to c++.

You're right about one should create libraries for most used functions but in .bat it could become more complex.

You might be interested in mingw as it can compile c, c++ under windows (that what i would use for creating libraries) and create more exe.

@Jaclaz

That was exactly why i said "you have to pass through another way". I knew i could parsed the ouput with a for command the as the variable was already set why not use it ?

[edisonx]

thank you , allen 2.

and sorry for I still have another question..

a simple code in C

/* pow.c , generate pow.exe */
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
int main(int argc, char **argv)
{
    if(argv!=3) return 1; 
    else printf("%lf", pow( atof(argv[1]), atof(argv[2])) );
    return 0;
}

:: demo.bat
pow.exe 1.23 4.56

it will show 2.570202 in console window. but I can't get it in batch-variable. I handle it by redirection to a file, then read the file again

:: demo.bat
SET c=0
pow.exe 1.23 4.56 > _rst.txt
FOR /F %%I IN ( _rst.txt) DO (
   SET c=%%I
)
del _rst.txt

I know, the method is slow and stupid. I just want to know , in batch file, is the method good ? or is any method better than this ?

------

As you said, I want to save the value into a variable,but in C language, it's a big problem, just like this

/* filename: pow2.c  generate: pow2.exe */
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
int main(int argc, char **argv)
{
    if(argv!=4) return 1; 
    else sprintf(argv[3],  "%lf",  pow( atof(argv[1]), atof(argv[2])) );
    return 0;
}

I can't do that!! the behavior is very dangerous in C. in batch file

@echo off
SET rst
call pow2.exe 1.23 4.56 rst
echo %rst%

those codes can't work , because pow2.exe receive argv by

argv[0]=pow2.exe

argv[1]=1.23

argv[2]=4.56

argv[3]=rst const string, not variable, I can't change its value!!

----

maybe, I should ask another question :

「how to pass the envionment variable to batch file in C ? 」

----

I know it's a big and studip problem,

but I just want to know ,

how can I write some application in C,

and batch file can using it.

Thanks for your replies.

[jaclaz]

@Jaclaz

That was exactly why i said "you have to pass through another way". I knew i could parsed the ouput with a for command the as the variable was already set why not use it ?

Yep , but in this case (since the thing producing the piped text is a batch and it's output is already an Environment Variable) only.

I thought it would have been useful the posted trick as a solution to the "generic" problem "my batch won't accept piped input" .

@edisonx

Please do READ my previous post.

You can pipe the output of your small program into a batch (if needed).

More generally you use a FOR loop like:

FOR /F "tokens=* delims=" %%A in ('pow.exe 1.23 4.56') DO SET myvar=%%A

jaclaz

[edisonx]

Hi, jaclaz

thank you for your replay.

I need some time to study and understand the code that you wrote .

and need some time to try those.

thank you very much, help me a lot !!

[edisonx]

Hi, dear jaclaz :

I try your code , it wroks fine "now" .

First, I use vc 2008 to compile my C code, there is something wrong !! (It generates execute file, but I can't use it normal).

But I use gcc to compile my C code, It's fine !!!! (so suprise !!)

I reboot my computer, re-compiler the same code by gcc and vc,

then , the batch works fine now.

next, I wonder to build all C math / string librarys and some floating operator to cmath.exe.

Just because batch can't cal floating and can't using array.

allen2, jaclaz,

thank you a lot.

you help me really very much.

again and again.