Execute a system command

In this task, the goal is to run either the ls system command, or the pause system command.

AppleScript

do shell script "ls" without altering line endings

C

Compiler: GCC 4.0.1

Platform: BSD

#include <stdlib.h>

int main()
{
    system("ls");
}

C++

Compiler: Visual C++ 2005

system("pause");

Haskell

Interpreter: GHCi 6.6

import System.Cmd

main = system "ls"

IDL

$ls

Will execute "ls" with output to the screen.

 spawn,"ls",result

will execute it and store the result in the string array "result".

 spawn,"ls",unit=unit

will execute it asynchronously and direct any output from it into the LUN "unit" from whence it can be read at any (later) time.

Objective-C

Compiler: GCC 4.0.1 (apple)

NSTask runs an external process with explicit path and arguments.

void runls()
{
    [[NSTask launchedTaskWithLaunchPath:@"/bin/ls"
        arguments:[NSArray array]] waitUntilExit];
}

If you need to run a system command, invoke the shell:

void runSystemCommand(NSString *cmd)
{
    [[NSTask launchedTaskWithLaunchPath:@"/bin/sh"
        arguments:[NSArray arrayWithObjects:@"-c", cmd, nil]]
        waitUntilExit];
}

Or use the C method above.

Perl

Interpreter: Per;

Note the use of grave quotes instead of "normal" single quotes.

my $results = `ls`;

Alternate system call

system "ls";

Python

Interpreter: Python 2.5

 import os
 code = os.system('ls') # Just execute the command, return a success/fail code
 output = os.popen('ls').read() # If you want to get the output data

or

Interpreter:Python 2.4 (and above)

 import subprocess
 output = subprocess.Popen('ls', shell=True, stdout=subprocess.PIPE).stdout
 print output.read()

Note: The latter is the preferred method for calling external processes, although cumbersome, it gives you finer control over the process.

UNIX Shell

UNIX shells are designed to run system commands as a default operation.

ls

If one wants to capture the command's standard output:

CAPTUREDOUTPUT=$(ls)