CODEWITHSUNDEEP
windowsbatch-filecmdpipe
Opera
Opera

Reputation: 25

pipe operator in batch script

Sorry if this is a duplicate question :-)

I got below line of code from a batch script. (script.bat)

echo %DATE% %TIME% some text ... >> %logfile% | c:\path\script1.bat >> %logfile%

What is the significance of pipe (|) symbol here?

The script.bat is working fine from command line (script.bat), and it is running script1.bat as well.

While running script.bat from scheduled task it intermittently failed to run script1.bat, exiting with errorlevel 1.

Anyone have any idea what this | doing here :-)

Upvotes: 3

Views: 6739

Answers (1)

dbenham
dbenham

Reputation: 130919

I'm assuming you know what pipes are normally used for. In your code, both sides of the pipe have their stdout redirected to a file. So the pipe is not fulfilling its normal purpose.

The way Windows implements pipes is to launch a new cmd thread for each side of the pipe.

In your case, the | is a quick and dirty way to instantiate parallel processing of the two commands.

Update

I just realized that both sides of the pipe are redirecting stdout to the same log file. That should never work, because only one cmd process (or thread) at a time can have the file open for write access. It certainly does not work for me from the command line. I get the following error: The process cannot access the file because it is being used by another process. The only way that does not fail is if logfile is set to nul.

If I had to guess, I think the original developer intended to use & instead of |. There is no reason to run a single ECHO statement in parallel with another batch script. It looks like the first statement is simply a timestamp.

I think your code should look like

echo %DATE% %TIME% some text ... >> %logfile% & call c:\path\script1.bat >> %logfile%

or better yet

>>%logfile% (
  echo %DATE% %TIME% some text ...
  call c:\path\script1.bat
)

Upvotes: 5

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