Get system command output: Difference between revisions
(→{{header|Tcl}}: + standard ml) |
|||
| Line 849: | Line 849: | ||
</pre> |
</pre> |
||
See also demo\capture_console.exw (needs a bit more work on linux) |
See also demo\capture_console.exw (needs a bit more work on linux) |
||
=={{header|Phixmonti}}== |
|||
<lang Phixmonti>"hostname.txt" var hname |
|||
"hostname > " hname chain cmd |
|||
hname "r" fopen |
|||
dup fgets print fclose |
|||
"del " hname chain cmd</lang> |
|||
=={{header|PicoLisp}}== |
=={{header|PicoLisp}}== |
||
Revision as of 18:02, 29 June 2020
You are encouraged to solve this task according to the task description, using any language you may know.
- Task
Execute a system command and get its output into the program. The output may be stored in any kind of collection (array, list, etc.).
- Related task
Ada
<lang Ada>with Ada.Text_IO; use Ada.Text_IO; with Ada.Characters.Latin_1; use Ada.Characters.Latin_1; with GNAT.Expect; use GNAT.Expect; with GNAT.OS_Lib; use GNAT.OS_Lib; with GNAT.String_Split; use GNAT.String_Split;
procedure System_Command is
Command : String := "ls -l"; Args : Argument_List_Access; Status : aliased Integer; Separators : constant String := LF & CR; Reply_List : Slice_Set;
begin
Args := Argument_String_To_List (Command);
-- execute the system command and get the output in a single string
declare
Response : String :=
Get_Command_Output
(Command => Args (Args'First).all,
Arguments => Args (Args'First + 1 .. Args'Last),
Input => "",
Status => Status'Access);
begin
Free (Args);
-- split the output in a slice for easier manipulation
if Status = 0 then
Create (S => Reply_List,
From => Response,
Separators => Separators,
Mode => Multiple);
end if;
end;
-- do something with the system output. Just print it out
for I in 1 .. Slice_Count (Reply_List) loop
Put_Line (Slice (Reply_List, I));
end loop;
end System_Command;</lang>
Aime
<lang aime>o_("-- ", sshell().plan("expr", "8", "*", "9").link.b_dump('\n'), " --\n");</lang>
- Output:
-- 72 --
AWK
<lang AWK> BEGIN {
# For Windows
out = system2var("dir")
print out
# Non-Windows
out = getline2var("ls -l")
print out
}
- For a Windows environment using system() method
function system2var(command ,tempfile, cmd, out, rec, data, i) {
tempfile = "C:\\TEMP\\TMP.TMP"
cmd = command " > " tempfile
system(cmd)
close(cmd)
while (getline rec < tempfile > 0) {
if ( ++i == 1 )
data = rec
else
data = data "\n" rec
}
return(data)
}
- If command returns an ERRNO function returns null string
function getline2var(command ,fish, scale, ship) {
command = command " 2>/dev/null"
while ( (command | getline fish) > 0 ) {
if ( ++scale == 1 )
ship = fish
else
ship = ship "\n" fish
}
close(command)
return ship
}</lang>
BaCon
<lang freebasic>' Get system command result$ = EXEC$("fortune") PRINT CHOP$(result$) PRINT "First word: " & TOKEN$(result$, 1)</lang>
- Output:
prompt$ ./get-system-command Little known fact about Middle Earth: The Hobbits had a very sophisticated computer network! It was a Tolkien Ring... First word: Little
Batch File
<lang dos> @echo off setlocal enabledelayedexpansion
- Without storing the output of the command, it can be viewed by inputting the command
dir
- Storing the output of 'dir' as "line[]" containing the respective lines of output (starting at line[1])
- Note: This method removes any empty lines from the output
set tempcount=0 for /f "tokens=*" %%i in ('dir') do (
set /a tempcount+=1 set "line!tempcount!=%%i"
)
- The array would be viewed like this
for /l %%i in (1,1,%tempcount%) do echo !line%%i!
- Storing the output of 'dir' in a file, then outputting the contents of the file to the screen
- NOTE: rewrites any file named "out.temp" in the current directory
dir>out.temp type out.temp del out.temp
pause>nul </lang>
C
<lang C>
- include <stdio.h>
- include <stdlib.h>
- include <string.h>
int main(int argc, char **argv) {
if (argc < 2) return 1;
FILE *fd; fd = popen(argv[1], "r"); if (!fd) return 1;
char buffer[256]; size_t chread; /* String to store entire command contents in */ size_t comalloc = 256; size_t comlen = 0; char *comout = malloc(comalloc);
/* Use fread so binary data is dealt with correctly */
while ((chread = fread(buffer, 1, sizeof(buffer), fd)) != 0) {
if (comlen + chread >= comalloc) {
comalloc *= 2;
comout = realloc(comout, comalloc);
}
memmove(comout + comlen, buffer, chread);
comlen += chread;
}
/* We can now work with the output as we please. Just print
* out to confirm output is as expected */
fwrite(comout, 1, comlen, stdout);
free(comout);
pclose(fd);
return 0;
} </lang>
C#
<lang csharp>using System;
namespace GetSystemCommandOutput {
class Program {
static void Main(string[] args) {
System.Diagnostics.Process process = new System.Diagnostics.Process();
System.Diagnostics.ProcessStartInfo startInfo = new System.Diagnostics.ProcessStartInfo();
startInfo.WindowStyle = System.Diagnostics.ProcessWindowStyle.Hidden;
startInfo.FileName = "cmd.exe";
startInfo.Arguments = "/c echo Hello World";
startInfo.RedirectStandardOutput = true;
startInfo.UseShellExecute = false;
process.StartInfo = startInfo;
process.Start();
string output = process.StandardOutput.ReadToEnd();
Console.WriteLine("Output is {0}", output);
}
}
}</lang>
C++
<lang cpp>#include <fstream>
- include <iostream>
std::string execute(const std::string& command) {
system((command + " > temp.txt").c_str());
std::ifstream ifs("temp.txt");
std::string ret{ std::istreambuf_iterator<char>(ifs), std::istreambuf_iterator<char>() };
ifs.close(); // must close the inout stream so the file can be cleaned up
if (std::remove("temp.txt") != 0) {
perror("Error deleting temporary file");
}
return ret;
}
int main() {
std::cout << execute("whoami") << '\n';
}</lang>
Clojure
sh returns a map of exit code, stdout, and stderr from the command: <lang clojure>(use '[clojure.java.shell :only [sh]]) (sh "echo" "Hello")</lang>
- Output:
{:exit 0, :out "Hello\n", :err ""}
Common Lisp
<lang lisp>(trivial-shell:shell-command "uname -imp")</lang>
- Output:
"x86_64 AMD A10-5750M APU with Radeon(tm) HD Graphics AuthenticAMD
We can also use functions specific to Common Lisp implementations. In SBCL, we have RUN-PROGRAM, which returns a process object. This object will contain an output stream if we use the :output keyword. We can then read from the stream:
<lang lisp>(defparameter *my-proc*
(sb-ext:run-program "mplayer" (list "/path/to/groovy/tune")
:search t :output :stream :wait nil))
(read-line (sb-ext:process-output *my-proc*) nil)</lang>
A bit more general, using uiop and grabbing output as a string: <lang lisp>(uiop:run-program '("ls" "-l" "-a") :output :string)</lang>
D
<lang D>import std.process; import std.stdio;
void main() {
auto cmd = executeShell("echo hello");
if (cmd.status == 0) {
writeln("Output: ", cmd.output);
} else {
writeln("Failed to execute command, status=", cmd.status);
}
}</lang>
- Output:
Output: hello
Factor
with-process-reader is a combinator that encapsulates reading the output of a system command. It also throws an error along with the appropriate exit status in the event of failure.
<lang factor>USING: io.encodings.utf8 io.launcher ;
"echo hello" utf8 [ contents ] with-process-reader .</lang>
- Output:
"hello\n"
FreeBASIC
<lang freebasic>' FB 1.05.0 Win64
'capture the output of the 'dir' command and print it to a text file
Open "dir_output.txt" For Output As #1 Open Pipe "dir" For Input As #2 Dim li As String
While Not Eof(2)
Line Input #2, li Print #1, li
Wend
Close #2 Close #1 End</lang>
Gambas
Click this link to run this code <lang gambas>Public Sub Main() Dim sStore As String
Shell "ls" To sStore Print sStore
End</lang>
Output:
1.txt 20150328 _204330.mp4 barcode.tar Business costs.ods cafe Charlie.fcstd code128.ttf Coffee icon.odg DBStore delete delete.csv Delete.lst delete's.txt ...
Genie
<lang genie>[indent=4] /*
Get system command output, in Genie
valac getSystemCommandOutput.gs ./getSystemCommandOutput
- /
init
try
// Blocking with output capture
standard_output : string
standard_error : string
exit_status : int
Process.spawn_command_line_sync("sh -c 'ls getSys*'",
out standard_output, out standard_error, out exit_status)
print standard_output
except e : SpawnError
stderr.printf("%s\n", e.message)</lang>
- Output:
Using an extra sh invocation, to limit the ls using file name expansion for the sample capture.
prompt$ valac getSystemCommandOutput.gs prompt$ ./getSystemCommandOutput getSystemCommandOutput getSystemCommandOutput.gs
Go
<lang go>package main
import (
"fmt" "log" "os/exec"
)
func main() {
output, err := exec.Command("ls", "-l").CombinedOutput()
if err != nil {
log.Fatal(err)
}
fmt.Print(string(output))
}</lang>
Haskell
<lang haskell>#!/usr/bin/env stack -- stack --resolver lts-8.15 --install-ghc runghc --package process
import System.Process (readProcess)
main :: IO () main = do
-- get the output of the process as a list of lines results <- lines <$> readProcess "hexdump" ["-C", "/etc/passwd"] "" -- print each line in reverse mapM_ (putStrLn . reverse) results</lang>
Icon and Unicon
<lang unicon>#
- piped.icn, Get system command output
- Dedicated to the public domain
procedure main()
# start with an empty list directory := []
# ls for UNIX, dir for other, assume Windows command := if &features == "UNIX" then "ls" else "dir"
# open command in pipe mode
p := open(command, "p") | stop("Cannot open pipe for ", command)
# read in results and append to list while put(directory, read(p))
# display the fifth entry, if there is one write(\directory[5])
close(p)
end</lang>
- Output:
prompt$ unicon -s piped.icn -x piped.u
IS-BASIC
<lang IS-BASIC>100 OPEN #1:"dirinfo.txt" ACCESS OUTPUT 110 SET DEFAULT CHANNEL 1 120 EXT "dir" 130 CLOSE #1 140 SET DEFAULT CHANNEL 0</lang>
J
We will box the result of uname -imp on a linux system, to show that we have captured the command output in J:
<lang J> require 'task'
<shell 'uname -imp'
┌─────────────────────┐ │x86_64 x86_64 x86_64 │ └─────────────────────┘</lang>
Caution: I have sometimes seen some versions of linux refuse to execute subshells after a few hundred thousand shell commands (the exec system call fails). I've not found any satisfying documentation on why this happens, but I strongly suspect kernel memory fragmentation (the examples where this happened were also using a lot of memory to accumulate results and it happened much more frequently an machines with little memory than on machines with more memory). Exiting J and starting a new process has cleared it up when it has happened. Anyways, I usually prefer to do that kind of processing before J starts, just to be safe.
(I've seen other problems on windows and osx - I am only singling out linux here because it is the most convenient for command line and system command use.)
Java
<lang java>import java.io.*; import java.util.*;
public class SystemCommand {
public static void main(String args[]) throws IOException {
String command = "cmd /c dir";
Process p = Runtime.getRuntime().exec(command);
try (Scanner sc = new Scanner(p.getInputStream())) {
System.out.printf("Output of the command: %s %n%n", command);
while (sc.hasNext()) {
System.out.println(sc.nextLine());
}
}
}
}</lang>
Output:
Output of the command: cmd /c dir
Het volume in station C heeft geen naam.
Het volumenummer is 10CE-30C3
Map van C:\projects\SystemCommand
30-06-2014 00:48 <DIR> .
30-06-2014 00:48 <DIR> ..
30-06-2014 00:48 <DIR> build
30-06-2014 00:46 3.624 build.xml
30-06-2014 00:48 <DIR> dist
30-06-2014 00:46 85 manifest.mf
30-06-2014 00:46 <DIR> nbproject
30-06-2014 00:46 <DIR> src
2 bestand(en) 3.709 bytes
6 map(pen) 756.833.009.664 bytes beschikbaar
Jsish
<lang javascript>var commandOutput = exec('ls -gocart', { retAll:true }); puts(commandOutput.data);</lang>
The jsish exec command (like many jsish commands) accepts an optional option object, details available with interactive help:
# help exec exec(val:string, options:string|object=void) Execute an OS command. If the command ends with '&', set the 'bg' option to true. The second argument can be a string, which is the same as setting the 'inputStr' option. By default, returns the string output, unless the 'bg', 'inputStr', 'retCode' or 'retAll' options are used [exec options] Option Type Description [Flags] ---------------------------------------------------------------------------- bg BOOL Run command in background using system() and return OS code. chdir STRING Change to directory. inputStr STRING Use string as input and return OS code. noError BOOL Suppress all OS errors. noRedir BOOL Disable redirect and shell escapes in command. noShell BOOL Do not use native popen which invokes via /bin/sh. trim BOOL Trim trailing whitespace from output. retAll BOOL Return the OS return code and data as an object. retCode BOOL Return only the OS return code.
With retAll the returned object has fields for .code, .status, .data.
The fifth element of the sample capture (ls -gocart) being:
# commandOutput.data.split('\n')[4];
-rw-rw-r--. 1 155 Feb 8 07:52 JSON.jsi
Julia
In a single string: <lang julia>ls = readstring(`ls`)</lang>
In multiple lines: <lang julia>ll = readlines(`ls -l`)</lang>
Kotlin
<lang scala>// version 1.0.6
import java.util.Scanner
fun main(args: Array<String>) {
val command = "cmd /c chcp" val p = Runtime.getRuntime().exec(command) val sc = Scanner(p.inputStream) println(sc.nextLine()) sc.close()
}</lang>
- Output:
Active code page: 850
LIL
The library from lil.c does not include a system command, but main.c for the lil shell does.
<lang tcl>set rc [system ls -go]</lang>
- Output:
prompt$ ./lil Little Interpreted Language Interactive Shell # set rc [system ls -go] total 1076 -rw-rw-r--. 1 729 Jan 14 2019 and.lil drwxrwxr-x. 3 4096 Jan 14 2019 atom -rw-rw-r--. 1 798 Jan 14 2019 call.lil -rw-rw-r--. 1 3079 Aug 4 22:44 catcher.lil drwxrwxr-x. 2 4096 Jan 14 2019 dll -rw-rw-r--. 1 593 Jan 14 2019 dollar.lil -rw-rw-r--. 1 697 Jan 14 2019 downeval.lil -rw-rw-r--. 1 904 Jan 14 2019 enveval.lil -rw-rw-r--. 1 1172 Jan 14 2019 expr.lil -rw-rw-r--. 1 180 Jan 14 2019 fileio.lil -rw-rw-r--. 1 427 Jan 14 2019 filter.lil drwxrwxr-x. 2 4096 Jan 14 2019 fplil -rw-rw-r--. 1 1369 Jan 14 2019 funcs.lil -rw-rw-r--. 1 49 Jan 14 2019 hello.lil -rw-rw-r--. 1 368 Jan 14 2019 jaileval.lil -rw-rw-r--. 1 214990 Aug 8 03:18 liblil.a -rw-rw-r--. 1 843 Jan 14 2019 liblil.tgt -rwxrwxr-x. 1 174216 Aug 8 03:18 lil -rw-rw-r--. 1 108062 Aug 8 03:18 lil.c -rw-rw-r--. 1 5963 Jan 14 2019 lil.h -rw-rw-r--. 1 214000 Aug 8 03:18 lil.o -rw-rw-r--. 1 108 Jan 14 2019 lil.pro -rw-rw-r--. 1 1244 Jan 14 2019 lil.tgt -rw-rw-r--. 1 362 Jan 14 2019 lil.wpj -rw-rw-r--. 1 666 Jan 14 2019 lists.lil -rw-rw-r--. 1 469 Jan 14 2019 local.lil -rw-rw-r--. 1 6082 Jan 14 2019 main.c -rw-rw-r--. 1 137440 Jul 26 12:29 main.o -rw-rw-r--. 1 968 Jan 14 2019 Makefile -rw-rw-r--. 1 455 Jan 14 2019 Makefile.bcc -rw-rw-r--. 1 1955 Jan 14 2019 mandelbrot.lil -rw-rw-r--. 1 603 Jan 14 2019 mkmsvc.bat -rw-rw-r--. 1 699 Jan 14 2019 mlcmt.lil -rw-rw-r--. 1 1653 Jan 14 2019 oop_animals.lil -rw-rw-r--. 1 1929 Jan 14 2019 oop.lil -rw-rw-r--. 1 57495 Jan 14 2019 readme.txt -rw-rw-r--. 1 811 Jan 14 2019 recfuncdef.lil -rw-rw-r--. 1 1231 Jan 14 2019 renamefunc.lil -rw-rw-r--. 1 333 Jan 14 2019 result.lil -rw-rw-r--. 1 310 Jan 14 2019 return.lil -rw-rw-r--. 1 1096 Jan 14 2019 robot.lil -rw-rw-r--. 1 2368 Jan 14 2019 sm.lil -rw-rw-r--. 1 1187 Jan 14 2019 strings.lil -rw-rw-r--. 1 813 Jan 14 2019 topeval.lil -rw-rw-r--. 1 615 Jan 14 2019 trim.lil -rw-rw-r--. 1 1720 Jan 14 2019 upeval.lil drwxrwxr-x. 2 4096 Jan 14 2019 vim -rw-rw-r--. 1 1995 Jan 14 2019 watch.lil # length $rc 2107
Lingo
<lang lingo>sx = xtra("Shell").new() put sx.shell_cmd("cd C:\dev\lsw\lib & dir")
-- " <snip> 31.08.2016 21:25 <DIR> . 31.08.2016 21:25 <DIR> .. 20.08.2016 04:58 <DIR> aes 23.06.2016 18:23 <DIR> audio 21.07.2016 19:19 <DIR> avmedia 23.06.2016 18:22 <DIR> base64 23.06.2016 18:21 <DIR> base9 <snip>"</lang>
Lua
<lang Lua>local output = io.popen("echo Hurrah!") print(output:read("*all"))</lang>
- Output:
Hurrah!
M2000 Interpreter
Make a UTF-16LE txt.out from dir using a new cmd with /U <lang M2000 Interpreter> Module CheckIt {
Dos "cd "+quote$(Dir$) +" & cmd /U /C dir *.txt >txt.out";
Document txt$
Repeat {
Wait 100
Try {
load.doc txt$, "txt.out"
}
} Until doc.len(txt$)<>0
Report txt$
} Checkit </lang>
Mathematica
<lang Mathematica>RunProcess["date"]</lang>
- Output:
<|"ExitCode" -> 0, "StandardOutput" -> "Wed Oct 4 14:01:01 BST 2017", "StandardError" -> ""|>
Neko
<lang ActionScript>/* Get system command output, neko */ var process_run = $loader.loadprim("std@process_run", 2); var process_stdout_read = $loader.loadprim("std@process_stdout_read", 4); var process_stderr_read = $loader.loadprim("std@process_stderr_read", 4); var process_stdin_close = $loader.loadprim("std@process_stdin_close", 1); var process_exit = $loader.loadprim("std@process_exit", 1); var sys_exit = $loader.loadprim("std@sys_exit", 1);
/* work buffer */ var bufsize = 1024; var buffer = $smake(bufsize);
/* default command is ls, otherwise pass command line arguments */ var argc = $asize($loader.args); var cmd = "ls"; var args;
/* Check command line arguments */ if argc > 0 {
cmd = $loader.args[0];
} if argc > 1 {
args = $asub($loader.args, 1, argc - 1);
}
/* spawn process, with arguments */ var proc = process_run(cmd, args);
/* Close input channel - command might be waiting for input */ process_stdin_close(proc);
/* capture and print stdout */ var not_done = true; var len = 0; do {
try {
len = process_stdout_read(proc, buffer, 0, bufsize);
} catch exc {
not_done = false;
}
if (not_done) $print($ssub(buffer, 0, len));
} while not_done;
/* capture and print any stderr */ not_done = true; len = 0; do {
try {
len = process_stderr_read(proc, buffer, 0, bufsize);
} catch exc {
not_done = false;
}
if (not_done) $print($ssub(buffer, 0, len));
} while not_done;
/* Get the exit status */ var ps = process_exit(proc); sys_exit(ps);</lang>
- Output:
prompt$ nekoc getcommand.neko prompt$ neko getcommand | tail -4 webbing.n xml ZipEx.hx zipper.n prompt$ neko getcommand ls -gocart | tail -4 -rw-rw-r--. 1 121 Sep 18 13:36 swap.neko -rw-rw-r--. 1 1513 Sep 18 18:32 getcommand.neko drwxr-xr-x. 15 4096 Sep 18 18:32 . -rw-rw-r--. 1 615 Sep 18 18:32 getcommand.n
Nim
<lang nim>import osproc
- Output string and error code
let (lsalStr, errCode) = execCmdEx("ls -al")
echo "Error code: " & $errCode echo "Output: " & lsalStr
- Output string only
let lsStr = execProcess("ls")
echo "Output: " & lsStr </lang>
Objeck
<lang objeck>class Test {
function : Main(args : String[]) ~ Nil {
output := System.Runtime->CommandOutput("ls -l");
each(i : output) {
output[i]->PrintLine();
};
}
} </lang>
ooRexx
version 1
<lang ooRexx>/* Execute a system command and retrieve its output into a stem. */
trace normal
/* Make the default values for the stem null strings. */
text. =
/* Issue the system command. "address command" is optional.) */
address command 'ls -l | rxqueue'
/* Remember the return code from the command. */
ls_rc = rc
/* Remember the number of lines created by the command. */
text.0 = queued()
/* Fetch each line into a stem variable. */
do t = 1 to text.0 parse pull text.t end
/* Output each line in reverse order. */
do t = text.0 to 1 by -1 say text.t end
/* Exit with the system command's return code. */ exit ls_rc</lang>
version 2
<lang oorexx>cmd='dir tu*.rex /od' cmd '| rxqueue' Say 'Output of "'cmd'"' Say Do While queued()>0
parse pull text Say text End </lang>
- Output:
Output of "dir tu*.rex /od"
Datenträger in Laufwerk I: ist USB DISK
Volumeseriennummer: 5D55-13AC
Verzeichnis von I:\
31.08.2016 19:36 1.358 turing.rex
31.08.2016 19:49 1.398 turing2.rex
2 Datei(en), 2.756 Bytes
0 Verzeichnis(se), 3.357.933.568 Bytes frei
version 3
<lang oorexx>dir='dir.dir' cmd='dir t*.rex /od' cmd '>'dir 'dir tu*.rex /od >'dir Say 'Output of "'cmd'"' Say Do While lines(dir)>0
Say linein(dir) End
Call lineout oid</lang>
- Output:
identical to version 2's output
PARI/GP
<lang parigp>externstr("time/t")</lang>
Perl
Uses the qx{} construct (which is a synonym for backticks, e.g. `command`) to execute a given command and redirect its output. A (somewhat contrived*) example, capturing only STDOUT: <lang perl>my @directories = grep { chomp; -d } `ls`; for (@directories) { chomp; ...; # Operate on directories }</lang>
- Perl's opendir function should be used in preference to parsing ls--it's safer, faster, and more portable.
Perl also honors shell redirections: <lang perl>my $command = shift or die "No command supplied\n"; my @output_and_errors = qx/$command 2>&1/ or die "Couldn't execute command\n";</lang> qx// is implemented internally with the built-in function readpipe, which can be invoked directly as readpipe EXPR (where EXPR is some command) and assigned to scalars or lists just like qx/command/ or `command`.
The open command can also be used to open pipes using the -| mode: <lang perl>use autodie; my $enc = ':encoding(UTF-8)'; my $child_pid = open(my $pipe, "-|$enc", 'ls'); while (<$pipe>) {
# Print all files whose names are all lowercase print if m/[^A-Z]+/;
}</lang>
Phix
<lang Phix>constant tmp = "hostname.txt",
cmd = iff(platform()=WINDOWS?"hostname":"uname -n")
{} = system_exec(sprintf("%s > %s",{cmd,tmp}),4) string host = trim(get_text(tmp)) {} = delete_file(tmp) ?host</lang>
- Output:
"Pete-PC"
See also demo\capture_console.exw (needs a bit more work on linux)
Phixmonti
<lang Phixmonti>"hostname.txt" var hname "hostname > " hname chain cmd hname "r" fopen dup fgets print fclose "del " hname chain cmd</lang>
PicoLisp
<lang PicoLisp>: (in '(uname "-om") (line T)) -> "aarch64 Android"</lang>
PowerShell
Capture system disk label information as an array of strings: <lang PowerShell> [string[]]$volume = cmd /c vol
$volume </lang>
- Output:
Volume in drive C is Ordo-Xenos Volume Serial Number is 8C33-162D
Python
<lang python>>>> import subprocess >>> returned_text = subprocess.check_output("dir", shell=True, universal_newlines=True) >>> type(returned_text) <class 'str'> >>> print(returned_text)
Volume in drive C is Windows Volume Serial Number is 44X7-73CE
Directory of C:\Python33
04/07/2013 06:40 <DIR> . 04/07/2013 06:40 <DIR> .. 27/05/2013 07:10 <DIR> DLLs 27/05/2013 07:10 <DIR> Doc 27/05/2013 07:10 <DIR> include 27/05/2013 07:10 <DIR> Lib 27/05/2013 07:10 <DIR> libs 16/05/2013 00:15 33,326 LICENSE.txt 15/05/2013 22:49 214,554 NEWS.txt 16/05/2013 00:03 26,624 python.exe 16/05/2013 00:03 27,136 pythonw.exe 15/05/2013 22:49 6,701 README.txt 27/05/2013 07:10 <DIR> tcl 27/05/2013 07:10 <DIR> Tools 16/05/2013 00:02 43,008 w9xpopen.exe
6 File(s) 351,349 bytes
9 Dir(s) 46,326,947,840 bytes free
>>> # Ref: https://docs.python.org/3/library/subprocess.html</lang>
R
<lang rsplus> system("wc -l /etc/passwd /etc/group", intern = TRUE) </lang>
- Output:
[1] " 49 /etc/passwd" " 80 /etc/group" " 129 total"
Racket
We use #lang racket/base to show which module system is in. It would be imported anyway if we use the larger #lang racket.
This demonstrates one function: system</system>. It is the simplest of a family of commands in the racket/system collection.
See documentation for system and friends.
<lang racket>#lang racket/base
(require racket/system
(only-in racket/port with-output-to-string)
tests/eli-tester)
(test
;; system runs command and outputs to current output port (which is stdout unless we catch it)
(system "ls /etc/motd") => #t
;; it throws an error on non-zero exit code (so I need to catch it in this error handler)
(system "false") => #f ; nothing printed to stdout/stderr
(system "ls /etc/mosh") => #f ; error report printed to stderr
;; output can be captured by redirecting stdout/stderr (which are known as current-output-port and
;; current-error-port in racket parlance).
;; the command printed a \n, so there is a newline captured by the system command
(with-output-to-string (λ () (system "ls /etc/motd"))) => "/etc/motd\n"
;; no \n is captured when none is captured
(with-output-to-string (λ () (system "echo -n foo"))) => "foo"
;; error is still not captured (it's still printed to stderr)
(with-output-to-string (λ () (system "echo -n foo; echo bar 1>&2"))) => "foo"
;; we can capture both with:
(let* ((out-str-port (open-output-string))
(err-str-port (open-output-string))
(system-rv
(parameterize ((current-output-port out-str-port) (current-error-port err-str-port))
(system "echo -n foo; echo bar 1>&2"))))
(values system-rv (get-output-string out-str-port) (get-output-string err-str-port)))
=> (values #t "foo" "bar\n"))</lang>
- Output:
/etc/motd
the following goes to standard error:
ls: /etc/mosh: No such file or directory
bar
and back to standard output:
7 tests passed
Raku
(formerly Perl 6)
If you don't want to execute it in shell (and you probably don't), then use this:
<lang perl6>say run($command, $arg1, $arg2, :out).out.slurp-rest;</lang>
Unfortunately, it is very long to type, but that is the only way to pass your variables as arguments safely.
You might be tempted to start using shell when you have to pipe something, but even in that case there is no need to do so. See this code:
<lang perl6>my $p1 = run 'echo', 'Hello, world', :out;
my $p2 = run 'cat', '-n', :in($p1.out), :out;
say $p2.out.slurp-rest;</lang>
See docs for more info.
If you really want to run something in shell and you understand potential security problems, then you can use qx// (interpolates environment variables) or qqx// (interpolates normally). See the docs for more info.
<lang perl6>say qx[dir]</lang>
- Output:
Find_URI_in_text.p6 History_variables.p6 K-d_tree.pl
Fractran.pl History_variables.pl XML_Input.p6
REXX
<lang rexx>/*REXX program executes a system command and displays the results (from an array). */
parse arg xxxCmd /*obtain the (system) command from CL.*/
trace off /*suppress REXX error msgs for fails. */
@.= 0 /*assign default in case ADDRESS fails.*/
address system xxxCmd with output stem @. /*issue/execute the command and parms. */
if rc\==0 then say copies('─', 40) ' return code ' rc " from: " xxxCmd
/* [↑] display if an error occurred.*/
do #=1 for @.0 /*display the output from the command. */
say strip(@.#, 'T') /*display one line at a time──►terminal*/
end /*#*/ /* [↑] displays all the output. */
exit 0 /*stick a fork in it, we're all done. */</lang>
- output from the executed command (under Windows/XP): dir g:sub*.2*
Volume in drive G is -----G-----
Volume Serial Number is 6826-1B4B
Directory of G:\
05/22/2012 08:27 30 SUBSET.2
05/24/2012 03:55 2,117,571 SUBSET.20
05/24/2012 03:55 1,132,068 SUBSET.21
05/24/2012 09:56 522,155 SUBSET.22
05/24/2012 09:56 193,293 SUBSET.23
05/24/2012 09:56 71,931 SUBSET.24
05/24/2012 09:56 15,995 SUBSET.25
05/24/2012 09:56 3,188 SUBSET.26
05/24/2012 09:56 471 SUBSET.27
9 File(s) 4,056,702 bytes
0 Dir(s) 18,252,660,736 bytes free
Ring
<lang ring>
system("dir C:\Ring\doc")
</lang>
Output:
Volume in drive C is Helyi lemez
Volume Serial Number is F0B2-B1C8
Directory of C:\Ring\doc
2016. 04. 05. 17:19 <DIR> .
2016. 04. 05. 17:19 <DIR> ..
2016. 04. 07. 07:44 3 276 076 Fayed_RingDoc_1.0.chm
2016. 04. 06. 19:00 5 371 211 Fayed_RingDoc_1.0.pdf
2 File(s) 8 647 287 bytes
2 Dir(s) 949 801 435 136 bytes free
Ruby
Many options, google exec or system or %x. Demonstrating backticks:
<lang ruby>str = `ls`
arr = `ls`.lines</lang>
Run BASIC
<lang runbasic>a$ = shell$("dir") ' Returns the directory info into a$
print a$ ' prints the directory
</lang>
Rust
<lang rust>use std::process::Command;
use std::io::{Write, self};
fn main() {
let output = Command::new("/bin/cat")
.arg("/etc/fstab")
.output()
.expect("failed to execute process");
io::stdout().write(&output.stdout);
}</lang>
Scala
<lang scala>import scala.io.Source
val command = "cmd /c echo Time at %DATE% %TIME%"
val p = Runtime.getRuntime.exec(command)
val sc = Source.fromInputStream(p.getInputStream)
println(sc.mkString)</lang>
Sidef
Using backticks:
<lang ruby>var output = `ls` # `output` is a string
var lines = `ls`.lines # `lines` is an array</lang>
Using pipes:
<lang ruby>var pipe = %p(ls) # same as: Pipe('ls')
var pipe_h = pipe.open_r # open the pipe for reading
var lines = [] # will store the lines of the output
pipe_h.each { |line| lines << line }</lang>
Stata
Redirect the output to a temporary file, then read its contents into a result macro r(out).
<lang stata>program shellout, rclass
tempfile f
tempname m
shell `0' > `f'
file open `m' using "`f'", read binary
file seek `m' eof
file seek `m' query
local n=r(loc)
if `n'>0 {
file seek `m' tof
file read `m' %`n's s
file close `m'
return local out "`s'"
}
end</lang>
Example:
<lang stata>. shellout dir /b *.dta
. display r(out)
auto.dta
titanium.dta
. shellout python -V
. display r(out)
Python 3.6.2</lang>
Swift
<lang Swift>import Foundation
let process = Process()
process.launchPath = "/usr/bin/env"
process.arguments = ["pwd"]
let pipe = Pipe()
process.standardOutput = pipe
process.launch()
let data = pipe.fileHandleForReading.readDataToEndOfFile()
let output = String.init(data: data, encoding: String.Encoding.utf8)
print(output!)</lang>
Standard ML
<lang Standard ML>val useOS = fn input =>
let
val text = String.translate (fn #"\"" => "\\\""|n=>str n ) input ;
val shellCommand = " echo " ^ text ^ "| gzip -c " ;
val fname = "/tmp/fConv" ^ (String.extract (Time.toString (Posix.ProcEnv.time()),7,NONE) );
val me = ( Posix.FileSys.mkfifo
(fname,
Posix.FileSys.S.flags [ Posix.FileSys.S.irusr,Posix.FileSys.S.iwusr ]
) ;
Posix.Process.fork ()
) ;
in
if (Option.isSome me) then
let
val fin =BinIO.openIn fname
in
( Posix.Process.sleep (Time.fromReal 0.1) ;
BinIO.inputAll fin before
(BinIO.closeIn fin ; OS.FileSys.remove fname )
)
end
else
( OS.Process.system ( shellCommand ^ " > " ^ fname ^ " 2>&1 " ) ;
Word8Vector.fromList [] before OS.Process.exit OS.Process.success
)
end;
</lang>
call
useOS "This is my text, zip it now" ;
val it =
fromList[0wx1F, 0wx8B, 0wx8, 0wx0, 0wxBE, 0wxCE, 0wx7F, 0wx5E, 0wx0, 0wx3,
...]: BinIO.vector
Tcl
The exec makes this straight-forward for most commands.
<lang tcl>set data [exec ls -l]
puts "read [string length $data] bytes and [llength [split $data \n]] lines"</lang>
There are a few exceptions, such as the DIR command on Windows, where they need to be run slightly differently due to being system shell builtins rather than executables. In that case, the auto_execok standard library command is used to look up how to run the command (strictly it can be used for any command — it will do path resolution, etc. — but is only necessary for system builtins).
<lang tcl>set data [exec {*}[auto_execok DIR]]</lang>
By default, Tcl will use the system encoding (as reported by encoding system) to understand the output byte-stream as characters, and will auto-convert all the various types of newline terminators into U+00000A characters. Control over this is possible by launching the subprocess as a pipe, configuring the pipe, and then reading the pipe in its entirety.
<lang tcl># This syntax is pretty ugly, alas
set pipe [open |[list ls -l] "r"]
fconfigure $pipe -encoding iso8859-1 -translation lf
set data [read $pipe]
close $pipe</lang>
This is usually not necessary except when dealing with binary data output.
Ursa
This program reads the output of the ifconfig command into the string stream 'output', then writes it to the screen.
<lang ursa>> decl iodevice iod
> decl string<> arg
> append "ifconfig" arg
> set iod (ursa.util.process.start arg)
> decl string<> output
> set output (iod.readlines)
> for (decl int i) (< i (size output)) (inc i)
.. out output endl console
..end for
lo0: flags=8049<UP,LOOPBACK,RUNNING,MULTICAST> mtu 16384
options=3<RXCSUM,TXCSUM>
inet6 ::1 prefixlen 128
inet 127.0.0.1 netmask 0xff000000
inet6 fe80::1%lo0 prefixlen 64 scopeid 0x1
nd6 options=1<PERFORMNUD>
gif0: flags=8010<POINTOPOINT,MULTICAST> mtu 1280
stf0: flags=0<> mtu 1280
en0: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500
options=27<RXCSUM,TXCSUM,VLAN_MTU,TSO4>
ether d4:9a:20:b8:8d:2c
nd6 options=1<PERFORMNUD>
media: autoselect
status: inactive
en1: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500
ether 00:26:08:e0:67:cc
inet6 fe80::226:8ff:fee0:67cc%en1 prefixlen 64 scopeid 0x5
inet 172.20.30.66 netmask 0xffffff00 broadcast 172.20.30.255
nd6 options=1<PERFORMNUD>
media: autoselect
status: active
fw0: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 4078
lladdr d4:9a:20:ff:fe:b8:8d:2c
nd6 options=1<PERFORMNUD>
media: autoselect <full-duplex>
status: inactive
p2p0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 2304
ether 02:26:08:e0:67:cc
media: autoselect
status: inactive
> </lang>
VBScript
This program implements a function that executes a DOS command and returns the output to the caller.
<lang vb>For Each line In ExecCmd("ipconfig /all")
Wscript.Echo line
Next
'Execute the given command and return the output in a text array.
Function ExecCmd(cmd)
'Execute the command
Dim wso : Set wso = CreateObject("Wscript.Shell")
Dim exec : Set exec = wso.Exec(cmd)
Dim res : res = ""
'Read all result text from standard output
Do
res = res & VbLf & exec.StdOut.ReadLine
Loop Until exec.StdOut.AtEndOfStream
'Return as a text array
ExecCmd = Split(Mid(res,2),vbLf)
End Function</lang>
Visual Basic .NET
<lang vbnet>Module Module1
Sub Main()
Dim proccess As New Process
Dim startInfo As New ProcessStartInfo
startInfo.WindowStyle = ProcessWindowStyle.Hidden
startInfo.FileName = "cmd.exe"
startInfo.Arguments = "/c echo Hello World"
startInfo.RedirectStandardOutput = True
startInfo.UseShellExecute = False
proccess.StartInfo = startInfo
proccess.Start()
Dim output = proccess.StandardOutput.ReadToEnd
Console.WriteLine("Output is {0}", output)
End Sub
End Module</lang>
zkl
From the REPL on Linux. Runs a command in the shell with stdout redirected to file, then slurps the file. A bit greasy since there isn't a way to find/generate a unique unused file name.
<lang zkl>zkl: System.cmd("date >foo.txt")
0 // date return code
zkl: File("foo.txt").read().text
Wed Aug 20 00:28:55 PDT 2014</lang>
- Programming Tasks
- Solutions by Programming Task
- Ada
- Aime
- AWK
- BaCon
- Batch File
- C
- C sharp
- C++
- Clojure
- Common Lisp
- Trivial-shell
- Uiop
- D
- Factor
- FreeBASIC
- Gambas
- Genie
- Go
- Haskell
- Process
- Icon
- Unicon
- IS-BASIC
- J
- Java
- Jsish
- Julia
- Kotlin
- LIL
- Lingo
- Shell Xtra
- Lua
- M2000 Interpreter
- Mathematica
- Neko
- Nim
- Objeck
- OoRexx
- PARI/GP
- Perl
- Phix
- Phixmonti
- PicoLisp
- PowerShell
- Python
- R
- Racket
- Raku
- REXX
- Ring
- Ruby
- Run BASIC
- Rust
- Scala
- Sidef
- Stata
- Swift
- Standard ML
- Tcl
- Ursa
- VBScript
- Visual Basic .NET
- Zkl