Reading input from a system command in Haskell

Question

hi I need to read ~~the command line~~ standard out after executing a haskell command, i know there are two modules to execute system commands: System.Cmd and System.Process

can anybody show me a simple example how to run the System.Process functions?

here is a example what i need to do (i know there is System.Directory to do that but i thought this is a good example):

execute a system command like ls -a
now i dont want the user to see the output
the output should only be accessable in my program to validate it

how can i do that?

I think you mean read a command's output, not read the command line. The command line means the name of the command being executed and its arguments. — Robin Green
– Robin Green, Commented May 20, 2011 at 14:44
The edit to the question is confusing. I interpreted the original as asking about reading the new process' standard out rather than in. — Anthony
– Anthony, Commented May 20, 2011 at 18:00

Anthony · Accepted Answer · 2019-09-05 15:35:50Z

20

import System.Process
test = readProcess "ls" ["-a"] ""

Do refer to the documentation for usage details.

edited Sep 5, 2019 at 15:35

answered May 20, 2011 at 14:40

Anthony

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3 Comments

Anthony Over a year ago

@Tarrasch The "ls" command is of course not platform independent, but readProcess should be. The documentation for System.Process mentions various areas where Windows' behavior deviates from the Unix-based platforms.

Stéphane Laurent Over a year ago

It's better to use readProcessWithExitCode.

user3827326 Over a year ago

Documentation link is dead, and this no solution no longer works.

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