Secure temporary file

Task

Create a temporary file, securely and exclusively (opening it such that there are no possible race conditions).

It's fine assuming local filesystem semantics (NFS or other networking filesystems can have signficantly more complicated semantics for satisfying the "no race conditions" criteria).

The function should automatically resolve name collisions and should only fail in cases where permission is denied, the filesystem is read-only or full, or similar conditions exist (returning an error or raising an exception as appropriate to the language/environment).

Ada

Ada creates a temporary file whenever the create procedure is called without file name. That temporary file is automatically deleted at the end of the program creating the file.

This example creates a temporary file, writes to the file, then reads from the file.

<lang ada>with Ada.Text_Io; use Ada.Text_Io;

procedure Temp_File is

  Temp : File_Type;
  Contents : String(1..80);
  Length : Natural;

begin

  -- Create a temporary file
  Create(File => Temp);
  Put_Line(File => Temp, Item => "Hello World");
  Reset(File => Temp, Mode => In_File);
  Get_Line(File => Temp, Item => Contents, Last => Length);
  Put_Line(Contents(1..Length));

end Temp_File;</lang>

BBC BASIC

Works with: BBC BASIC for Windows

The file is automatically deleted when closed. <lang bbcbasic> file% = FNopentempfile

     IF file% = 0 ERROR 100, "Failed to open temp file"
     PRINT #file%, "Hello world!"
     PTR#file% = 0
     INPUT #file%, message$
     CLOSE #file%
     PRINT message$
     END
     
     DEF FNopentempfile
     LOCAL pname%, hfile%, chan%
     OPEN_EXISTING = 3
     FILE_FLAG_DELETE_ON_CLOSE = &4000000
     GENERIC_READ = &80000000
     GENERIC_WRITE = &40000000
     INVALID_HANDLE_VALUE = -1
     DIM pname% LOCAL 260
     FOR chan% = 5 TO 12
       IF @hfile%(chan%) = 0 EXIT FOR
     NEXT
     IF chan% > 12 THEN = 0
     SYS "GetTempFileName", @tmp$, "BBC", 0, pname%
     SYS "CreateFile", $$pname%, GENERIC_READ OR GENERIC_WRITE, 0, 0, \
     \                 OPEN_EXISTING, FILE_FLAG_DELETE_ON_CLOSE, 0 TO hfile%
     IF hfile% = INVALID_HANDLE_VALUE THEN = 0
     @hfile%(chan%) = hfile%
     = chan%</lang>

Output:

Hello world!

C

<lang c>#include <stdlib.h>

include <stdio.h>

int main(void) {

 FILE *fh = tmpfile(); /* file is automatically deleted when program exits */
 /* do stuff with stream "fh" */
 fclose(fh);
 /* The C standard library also has a tmpnam() function to create a file
   for you to open later. But you should not use it because someone else might
   be able to open the file from the time it is created by this function to the
   time you open it. */
 return 0;

}</lang>

The following

Works with: POSIX

<lang c>#include <stdlib.h>

include <stdio.h>

int main(void) {

 char filename[] = "/tmp/prefixXXXXXX";
 int fd = mkstemp(filename);
 puts(filename);
 /* do stuff with file descriptor "fd" */
 close(fd);
 return 0;

}</lang>

C#

<lang csharp>using System; using System.IO;

Console.WriteLine(Path.GetTempFileName());</lang>

Clojure

It is good practice to explicitly delete temp files immediately once they've been used. <lang clojure>(let [temp-file (java.io.File/createTempFile "pre" ".suff")]

 ; insert logic here that would use temp-file
 (.delete temp-file))</lang>

D

Works with: Tango

<lang d>module tempfile ; import tango.io.TempFile, tango.io.Stdout ;

void main(char[][] args) {

 // create a temporary file that will be deleted automatically when out of scope
 auto tempTransient = new TempFile(TempFile.Transient) ;
 Stdout(tempTransient.path()).newline ;

 // create a temporary file, still persist after the TempFile object has been destroyed
 auto tempPermanent = new TempFile(TempFile.Permanent) ;
 Stdout(tempPermanent.path()).newline ;

 // both can only be accessed by the current user (the program?).

}</lang>

Delphi

Library: System.SysUtils

Library: System.IOUtils

<lang Delphi> program Secure_temporary_file;

{$APPTYPE CONSOLE}

uses

 System.SysUtils,
 System.IOUtils;

var

 FileName, buf: string;

begin

 FileName := TPath.GetTempFileName;
 with TFile.Open(FileName, TFileMode.fmCreate, TFileAccess.faReadWrite,
   Tfileshare.fsNone) do
 begin
   buf := 'This is a exclusive temp file';
   Write(buf[1], buf.Length * sizeof(char));
   Free;
 end;

 writeln(FileName);
 Readln;

end.</lang>

Emacs Lisp

make-temp-file creates a new empty temporary file, with perms "0700" so read-write to the current user only.

<lang Lisp>(make-temp-file "prefix") => "/tmp/prefix25452LPe"</lang>

make-temp-file is available in GNU Emacs 21 up, but not XEmacs 21.4. The Gnus included with XEmacs 21.4 has an mm-make-temp-file in its mm-util.el, or the APEL library can supply a make-temp-file (and for Emacs 20 too).

Fortran

Supposing F is an integer variable, whose value might be 10. This is the I/O unit number, and would be used in READ(F,etc. and WRITE(F,etc. statements. <lang Fortran> OPEN (F,STATUS = 'SCRATCH') !Temporary disc storage.</lang> Other attributes might be specified depending on the intended usage, but note that no file name is given. When the file is closed, its storage vanishes back to the file system.

Following the OPEN statement with INQUIRE (F,NAME = FNAME); WRITE (6,*) FNAME yields C:\DOCUME~1\Nicky\LOCALS~1\Temp\FOR57.tmp which is the DOS style short (8.3) file name for C:\Documents and Settings\Nicky\Local Settings\Temp\FOR57.tmp and the example's numerical value of 57 will be different on another run. Thus, the file could be interfered with, except that a file opened with WRITE access is exclusive-use, and there is no point in opening a SCRATCH file with READONLY (to allow sharing) because it cannot be a pre-existing disc file. However, the actual behaviour of a particular file system and compiler may or may not support such refinements as shared access as implied by non-standard keywords as READONLY, etc.

Go

Use ioutil.TempFile <lang go>package main

import ( "fmt" "io/ioutil" "log" "os" )

func main() { f, err := ioutil.TempFile("", "foo") if err != nil { log.Fatal(err) } defer f.Close()

// We need to make sure we remove the file // once it is no longer needed. defer os.Remove(f.Name())

// … use the file via 'f' … fmt.Fprintln(f, "Using temporary file:", f.Name()) f.Seek(0, 0) d, err := ioutil.ReadAll(f) if err != nil { log.Fatal(err) } fmt.Printf("Wrote and read: %s\n", d)

       // The defer statements above will close and remove the
       // temporary file here (or on any return of this function).

}</lang>

Output:

Wrote and read: Using temporary file: /tmp/foo054003078

Groovy

<lang groovy>def file = File.createTempFile( "xxx", ".txt" )

// There is no requirement in the instructions to delete the file. //file.deleteOnExit()

println file</lang>

Output:

C:\DOCUME~1\ROGER~1.GLO\LOCALS~1\Temp\xxx8918700806071036530.txt

Haskell

<lang haskell>import System.IO

main = do (pathOfTempFile, h) <- openTempFile "." "prefix.suffix" -- first argument is path to directory where you want to put it

         -- do stuff with it here; "h" is the Handle to the opened file
         return ()</lang>

HicEst

<lang HicEst>! The "scratch" option opens a file exclusively for the current process. ! A scratch file is automatically deleted upon process termination.

OPEN( FIle='TemporaryAndExclusive', SCRatch, IOStat=ErrNr) WRITE(FIle='TemporaryAndExclusive') "something" WRITE(FIle='TemporaryAndExclusive', CLoSe=1) ! explicit "close" deletes file

! Without "scratch" access can be controlled by "denyread", "denywrite", "denyreadwrite" options.

OPEN( FIle='DenyForOthers', DenyREAdWRIte, IOStat=ErrNr) WRITE(FIle='DenyForOthers') "something" WRITE(FIle='DenyForOthers', DELETE=1)</lang>

Icon and Unicon

A posix-based solution that works in both languages:

<lang unicon>procedure main()

   write("Creating: ",fName := !open("mktemp","rp"))
   write(f := open(fName,"w"),"Hello, world")
   close(f)

end</lang>

Java

<lang java>import java.io.File; import java.io.IOException;

public class CreateTempFile {

   public static void main(String[] args)  {
       try {
           //create a temp file
           File temp = File.createTempFile("temp-file-name", ".tmp");
           System.out.println("Temp file : " + temp.getAbsolutePath());
       }
       catch(IOException e) {
           e.printStackTrace();
   	}
   }

}</lang>

Julia

Works with: Linux

On Unix systems, Julia calls mkstemp to securely open a temporary file. This is likely multi-thread safe, check your system documentation for verification. This code should also work on Windows, but I've not verified that.

<lang Julia> msg = "Rosetta Code, Secure temporary file, implemented with Julia."

(fname, tio) = mktemp() println(fname, " created as a temporary file.") println(tio, msg) close(tio) println("\"", msg, "\" written to ", fname) </lang> Files written to \tmp persist for the login session, and are thus truly temporary. If the environment variable TMPDIR is set, the temporary file is created in this directory. In this case, the file may not be properly temporary. <lang Julia> ENV["TMPDIR"] = pwd() (fname, tio) = mktemp() println(fname, " created as a \"temporary\" file.") println(tio, msg) close(tio) println("\"", msg, "\" written to ", fname) </lang>

Output:

/tmp/tmphe0qlu created as a temporary file.
"Rosetta Code, Secure temporary file, implemented with Julia." written to /tmp/tmphe0qlu
/home/mike/rosetta/julia/tmpVNGK8D created as a "temporary" file.
"Rosetta Code, Secure temporary file, implemented with Julia." written to /home/joeb/rosetta/julia/tmpVNGK8D
$ cat /tmp/tmphe0qlu
Rosetta Code, Secure temporary file, implemented with Julia.
$ ls -l /tmp/tmphe0qlu
-rw------- 1 joeb joeb 61 Apr 13 13:18 /tmp/tmphe0qlu
$ cat tmpVNGK8D
Rosetta Code, Secure temporary file, implemented with Julia.
$ ls -l tmpVNGK8D
-rw------- 1 joeb jeob 61 Apr 13 13:18 tmpVNGK8D

Kotlin

<lang scala>// version 1.1.2

import java.io.File

fun main(args: Array<String>) {

   try {
       val tf = File.createTempFile("temp", ".tmp")
       println(tf.absolutePath)
       tf.delete()
   }
   catch (ex: Exception) {
       println(ex.message)
   }

}</lang> Sample output (Ubuntu v14.04):

Output:

/tmp/temp1551492276377305257.tmp

Lua

<lang lua>fp = io.tmpfile()

-- do some file operations

fp:close()</lang>

M2000 Interpreter

tmp files automatic deleted when Environment end (per running environment)

<lang M2000 Interpreter> Module Checkit {

     \\ we get a tempname$ choosed  from Windows
     a$=tempname$
     Try ok  {
           \\ we can use wide to export in utf-16le
           \\ without wide we export as Ansi (set Local to desired language)
           Rem Locale 1033 ' when no use of wide
           Open a$ for wide output exclusive as #f
                 wait 10
                 \\ Notepad can't open, because we open it for exclusive use
                 Win "Notepad", a$     
                 Print  #f, "something"
                 Print "Press a key";Key$
           Close #f
     }
     If error or not ok then Print Error$
     Win "Notepad", a$

} Checkit

</lang>

Mathematica/Wolfram Language

<lang Mathematica>tmp = OpenWrite[] Close[tmp]</lang>

Nanoquery

<lang Nanoquery>import Nanoquery.IO

def guaranteedTempFile() // create a file object to generate temp file names $namegen = new(File)

// generate a temp filename $tempname = $namegen.tempFileName()

// file names are generated with uuids so they shouldn't repeat // in the case that they do, generate new ones until the generated // filename is unique $tempfile = new(File, $tempname) while ($tempfile.exists()) $tempname = $namegen.tempFileName() $tempfile = new(File, $tempname) end

// create the file and lock it from writing $tempfile.create() lock $tempfile.fullPath()

// return the file reference return $tempfile end</lang>

NetRexx

This example is incomplete. JVM Windows related bug workaround JDK-4715154 Please ensure that it meets all task requirements and remove this message.

<lang NetRexx>/* NetRexx */

options replace format comments java crossref symbols binary

runSample(arg) return

-- . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . method makeTempFile(prefix = String, suffix = String null, startDir = String null) -

 public static signals IOException returns File
 if startDir \= null then fStartDir = File(startDir)
 else                     fStartDir = null
 ff = File.createTempFile(prefix, suffix, fStartDir)
 ff.deleteOnExit() -- make sure the file is deleted at termination
 return ff

-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ method runSample(arg) private static

 do
   tempFiles = [ -
     makeTempFile('rexx'), -
     makeTempFile('rexx', '.rex'), -
     makeTempFile('rexx', null, './tmp') -
   ]
   loop fFile over tempFiles
     fName = fFile.getCanonicalPath()
     say 'Temporary file:' fName
     end fFile
 catch ex = IOException
   ex.printStackTrace()
 end
 return

</lang>

Nim

<lang nim>import posix_utils, os, strutils var (filename, f) = mkstemp("tmp") echo("$1 created"%filename) f.writeLine("This is a secure temporary file.") f.close() for line in lines(filename):

 echo(line)

removeFile(filename)</lang>

Output:

tmpAYStx6 created
This is a secure temporary file.

OCaml

From the module Filename, one can use the functions temp_file or open_temp_file <lang ocaml># Filename.temp_file "prefix." ".suffix" ;; - : string = "/home/blue_prawn/tmp/prefix.301f82.suffix"</lang>

Octave

Octave has several related functions <lang Matlab> [FID, MSG] = tmpfile(); % Return the file ID corresponding to a new temporary

 filename = tmpnam (...);   % generates temporary file name, but does not open file
 [FID, NAME, MSG] = mkstemp (TEMPLATE, DELETE);    % Return the file ID corresponding to a new temporary file with a unique name created from TEMPLATE.</lang>

Pascal

Works with: Free_Pascal

Library: SysUtils

<lang pascal>Program TempFileDemo;

uses

 SysUtils;

var

 tempFile: text;

begin

 assign (Tempfile, GetTempFileName);
 rewrite (tempFile);
 writeln (tempFile, 5);
 close (tempFile);

end.</lang>

Perl

function interface: <lang perl>use File::Temp qw(tempfile); $fh = tempfile(); ($fh2, $filename) = tempfile(); # this file stays around by default print "$filename\n"; close $fh; close $fh2;</lang>

object-oriented interface: <lang perl>use File::Temp; $fh = new File::Temp; print $fh->filename, "\n"; close $fh;</lang>

Phix

The temp_file() function (see builtins/pfile.e) can be used for this: <lang Phix>pp(temp_file()) {integer fn, string name} = temp_file("myapp/tmp","data","log","wb") pp({fn,name}) close(fn) {} = delete_file(name)</lang>

Output:

`C:\Users\Pete\AppData\Local\Temp\419750.tmp`
{3, `C:\Program Files (x86)\Phix\myapp\tmp\data408865.log`}

If you don't provide an open mode (one of "w", "wb", "a", or "ab") then there is a 1-in-a-million chance someone else will beat you to the punch; if you do provide one, it will open/loop for you.

PHP

<lang php>$fh = tmpfile(); // do stuff with $fh fclose($fh); // file removed when closed

// or: $filename = tempnam('/tmp', 'prefix'); echo "$filename\n"; // open $filename and do stuff with it</lang>

PicoLisp

The 'tmp' function returns temporary file names which are exclusively for the current process (based on the process ID). These files are automatically deleted upon process termination. Background tasks within a single PicoLisp process is always non-preemptive, therefore dedicated locks are usually not necessary. If they are (e.g. because such a file name is passed to a child process), explicit locks with the 'ctl' functions are possible. <lang PicoLisp>: (out (tmp "foo") (println 123)) # Write tempfile -> 123

(in (tmp "foo") (read)) # Read tempfile

-> 123

(let F (tmp "foo")

  (ctl F                                 # Get exclusive lock
     (in F 
        (let N (read)                    # Atomic increment
           (out F (println (inc N))) ) ) ) )

-> 124</lang>

PowerShell

<lang PowerShell> $tempFile = [System.IO.Path]::GetTempFileName() Set-Content -Path $tempFile -Value "FileName = $tempFile" Get-Content -Path $tempFile Remove-Item -Path $tempFile </lang>

Output:

FileName = C:\Users\Owner\AppData\Local\Temp\tmpB68.tmp

PureBasic

<lang PureBasic>Procedure.s TempFile()

 Protected a, Result$

 For a = 0 To 9999
   Result$ = GetTemporaryDirectory() + StringField(GetFilePart(ProgramFilename()),1,".")
   Result$ + "_" + Str(ElapsedMilliseconds()) + "_(" + RSet(Str(a),4,"0") + ").tmp"
   If FileSize(Result$) = -1                                      ;  -1 = File not found
     ProcedureReturn Result$
   EndIf
 Next

 ProcedureReturn ""

EndProcedure

Define File, File$

File$ = TempFile() If File$ <> ""

 File = CreateFile(#PB_Any, File$)
 If File <> 0
   WriteString(File, "Some temporary data here...")
   CloseFile(File)
 EndIf

EndIf</lang>

Python

Works with: Python version 2.3+

In both cases, the temporary file will be deleted automatically when the file is closed. The invisible file will not be accessible on UNIX-like systems. You can use os.link to preserve the visible temporary file contents.

<lang python>>>> import tempfile >>> invisible = tempfile.TemporaryFile() >>> invisible.name '<fdopen>' >>> visible = tempfile.NamedTemporaryFile() >>> visible.name '/tmp/tmpZNfc_s' >>> visible.close() >>> invisible.close()</lang>

More low level way, if you have special needs. This was the only option before Python 2.3:

<lang python>fd, path = tempfile.mkstemp() try:

   # use the path or the file descriptor

finally:

   os.close(fd)</lang>

Racket

lang racket

(make-temporary-file) </lang>

Raku

(formerly Perl 6)

Works with: Rakudo version 2017.09

This is something best done with a module which is heavily tested, tries to account for all corner cases and automatically cleans up after itself.

Almost verbatim from the synopsis: <lang perl6>use File::Temp;

Generate a temp file in a temp dir

my ($filename0,$filehandle0) = tempfile;

specify a template for the filename
* are replaced with random characters

my ($filename1,$filehandle1) = tempfile("******");

Automatically unlink files at DESTROY (this is the default)

my ($filename2,$filehandle2) = tempfile("******", :unlink);

Specify the directory where the tempfile will be created

my ($filename3,$filehandle3) = tempfile(:tempdir("/path/to/my/dir"));

don't unlink this one

my ($filename4,$filehandle4) = tempfile(:tempdir('.'), :!unlink);

specify a prefix, a suffix, or both for the filename

my ($filename5,$filehandle5) = tempfile(:prefix('foo'), :suffix(".txt"));</lang>

REXX

REXX uses the underlying OS to create and delete the file. <lang rexx>/*REXX pgm secures (a temporary file), writes to it, displays the file, then deletes it.*/ parse arg tFID # . /*obtain optional argument from the CL.*/ if tFID== | tFID=="," then tFID= 'TEMP.FILE' /*Not specified? Then use the default.*/ if #== | #=="," then #= 6 /* " " " " " " */ call lineout tFID /*insure file is closed. */ rc= 0 say '··· creating file: ' tFID call lineout tFID,,1 /*insure file is open and at record 1. */ if rc\==0 then call ser rc 'creating file' tFID /*issue error if can't open the file. */ say '··· writing file: ' tFID

   do j=1  for #                                /*write a half-dozen records to file.  */
   call lineout tFID, 'line' j                  /*write a  record  to the file.        */
   if rc\==0  then call ser rc 'writing file'  tFID    /*Have an error?  Issue err msg.*/
   end   /*j*/

call lineout tFID /*close the file. */ say '··· reading/display file: ' tFID

   do j=1  while lines(tFID)>0                  /*read the entire file and display it. */
   x= linein(tFID)                              /*read a record from the file.         */
   if rc\==0  then call ser rc 'reading file'  tFID    /*Have an error?  Issue err msg.*/
   say 'line ' j  " of file" tFID":"  x                /*display a record to the term. */
   end   /*j*/

call lineout tFID /*close the file. */ say '··· erasing file: ' tFID 'ERASE' tFID /*erase the file. */ exit 0 /*stick a fork in it, we're all done. */ /*──────────────────────────────────────────────────────────────────────────────────────*/ ser: say; say '***error***' arg(1); say; exit 13 /*issue an error message to the term. */</lang>

output when using the default input:

··· creating file:  TEMP.FILE
··· writing  file:  TEMP.FILE
··· reading/display file:  TEMP.FILE
line  1  of file TEMP.FILE: line 1
line  2  of file TEMP.FILE: line 2
line  3  of file TEMP.FILE: line 3
line  4  of file TEMP.FILE: line 4
line  5  of file TEMP.FILE: line 5
line  6  of file TEMP.FILE: line 6
··· erasing file:  TEMP.FILE

Ruby

<lang ruby>irb(main):001:0> require 'tempfile' => true irb(main):002:0> f = Tempfile.new('foo') => #<File:/tmp/foo20081226-307-10p746n-0> irb(main):003:0> f.path => "/tmp/foo20081226-307-10p746n-0" irb(main):004:0> f.close => nil irb(main):005:0> f.unlink => #<Tempfile: (closed)></lang>

Rust

<lang rust>// 202100322 Rust programming solution

use tempfile::tempfile;

fn main() {

   let fh = tempfile();

   println!("{:?}", fh);

}</lang>

Output:

Ok(File { fd: 3, path: "/tmp/#37224506 (deleted)", read: true, write: true })

Scala

<lang scala>import java.io.{File, FileWriter, IOException}

 def writeStringToFile(file: File, data: String, appending: Boolean = false) =
   using(new FileWriter(file, appending))(_.write(data))

 def using[A <: {def close() : Unit}, B](resource: A)(f: A => B): B =
   try f(resource) finally resource.close()

 try {
   val file = File.createTempFile("_rosetta", ".passwd")
   // Just an example how you can fill a file
   using(new FileWriter(file))(writer => rawDataIter.foreach(line => writer.write(line)))
   scala.compat.Platform.collectGarbage() // JVM Windows related bug workaround JDK-4715154
   file.deleteOnExit()
   println(file)
 } catch {
   case e: IOException => println(s"Running Example failed: ${e.getMessage}")
 }</lang>

Sidef

<lang ruby>var tmpfile = require('File::Temp'); var fh = tmpfile.new(UNLINK => 0); say fh.filename; fh.print("Hello, World!\n"); fh.close;</lang>

Standard ML

<lang sml>val filename = OS.FileSys.tmpName ();</lang>

Tcl

Works with: Tcl version 8.6

Will store the name of the file in the variable filenameVar and an open read-write channel on the file in the variable chan. <lang Tcl>set chan [file tempfile filenameVar]</lang> Note that because we're asking for the filename in the script, Tcl does not automatically clean the file. (There are cases where auto-cleaning would be really unwanted.) If we hadn't asked for it, the file would be automatically deleted (at a time that depends on platform constraints).

TUSCRIPT

<lang tuscript> $$ MODE TUSCRIPT tmpfile="test.txt" ERROR/STOP CREATE (tmpfile,seq-E,-std-) text="hello world" FILE $tmpfile = text - tmpfile "test.txt" can only be accessed by one user an will be deleted upon programm termination </lang>

UNIX Shell

UNIX shell scripts cannot guarantee secure, race-free, exclusive access to an open file descriptor. The best approach to working around this limitation is to create a directory (the mkdir command is a wrapper around the atomic mkdir() system call) and then perform all temporary file operations thereunder.

<lang bash>RESTOREUMASK=$(umask) TRY=0 while :; do

  TRY=$(( TRY + 1 ))
  umask 0077
  MYTMP=${TMPDIR:-/tmp}/$(basename $0).$$.$(date +%s).$TRY
  trap "rm -fr $MYTMP" EXIT
  mkdir "$MYTMP" 2>/dev/null && break

done umask "$RESTOREUMASK" cd "$MYTMP" || {

  echo "Temporary directory failure on $MYTMP" >&2
  exit 1; }</lang>

Note that the shell special variable $$ (the PID of the currently exec()-ed shell) is unique at any given moment on a UNIX system, and $(date +%s) gives the time represented as a number of seconds since the UNIX epoch (GNU date or any other with the %s extension). So any name collision here is most likely "enemy action." This code will loop, picking new names and resetting the trap (clean-up command) until it succeeds in making a directory. (Simple changes to the code could limit the number of attempts or implement a timeout).

Wren

Library: Wren-ioutil

Library: Wren-fmt

<lang ecmascript>import "random" for Random import "/ioutil" for File, FileUtil import "/fmt" for Fmt

var rand = Random.new()

var createTempFile = Fn.new { |lines|

   var tmp
   while (true) {
       // create a name which includes a random 6 digit number
       tmp = "/tmp/temp%(Fmt.swrite("$06d", rand.int(1e6))).tmp"
       if (!File.exists(tmp)) break
   }
   FileUtil.writeLines(tmp, lines)
   return tmp

}

var lines = ["one", "two", "three"] var tmp = createTempFile.call(lines) System.print("Temporary file path: %(tmp)") System.print("Original contents of temporary file:") System.print(File.read(tmp))

// append some more lines var lines2 = ["four", "five", "six"] FileUtil.appendLines(tmp, lines2) System.print("Updated contents of temporary file:") System.print(File.read(tmp)) File.delete(tmp) System.print("Temporary file deleted.")</lang>

Output:

Sample run:

Temporary file path: /tmp/temp574327.tmp
Original contents of temporary file:
one
two
three

Updated contents of temporary file:
one
two
three
four
five
six

Temporary file deleted.

zkl

zkl uses the underlying OS to create these files, mkstemp (POSIX), _mktemp_s (Windows). Not at all sure Windows is race free however.

Output:

zkl: File.mktmp()
File(zklTmpFile082p1V)