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learntolive
learntolive

Reputation: 1

escaping characters in batch using ^

I can get a proper output wuth the below command in the command prompt, tasklist /fi "imagename ne siebde*" /fi "imagename eq sieb*" /svc | find "gtwyns".

But if i want to use this condition in batch files i have to do this with the below command.

for /f "tokens=2 delims= " %%a in ('tasklist /fi "imagename ne siebde*" /fi "imagename eq sieb*" /svc ^| find "gtwyns")

I need to understand the function of ^ character and how does it work actually?

I also wanna know does it open a new cmd when wi use a pipe in batch script?

Upvotes: 0

Views: 159

Answers (1)

JosefZ
JosefZ

Reputation: 30258

Read FOR /F: loop command against the results of another command syntax:

FOR /F ["options"] %%parameter IN ('command_to_process') DO command
…
command_to_process : The output of the 'command_to_process' is passed 
                     into the FOR parameter.

… The command_to_process can be almost any internal or external command.

Almost any internal or external command (but the only command).

Now, read redirection syntax:

commandA | commandB Pipe the output from commandA into commandB

For instance, in wrong for /F "delims=" %%a in ('dir /B | sort /R') do echo %%~a
with unescaped | pipe:

  • commandA evaluates to for /F "delims=" %%a in ('dir /B and
  • commandB evaluates to sort /R') do echo %%~a although separate dir /B | sort /R is right command.

Hence, we need to escape (all) &, |, <, > redirection characters and (sometimes) " double quotes as follows (both ways are equivalent parsing dir /B "*.vbs" 2>NUL | sort /R command):

for /F "delims=" %%a in (' dir /B  "*.vbs" 2^>NUL ^| sort /R ') do echo %%~a
for /F "delims=" %%a in ('"dir /B ""*.vbs"" 2>NUL  | sort /R"') do echo %%~a

Therefore, next two loops should work the same way:

for /f "tokens=2 delims= " %%a in ('
    tasklist /fi "imagename ne siebde*" /fi "imagename eq sieb*" /svc ^| find "gtwyns"
  ') do echo set pid_ns=%%a

and 

for /f "tokens=2 delims= " %%a in ('
  "tasklist /fi ""imagename ne siebde*"" /fi ""imagename eq sieb*"" /svc | find ""gtwyns"""
') do echo set pid_ns=%%a

Upvotes: 2

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