Abandon this program to run another

Daftar Isi

• exec LIST

• exec PROGRAM LIST

  The exec function executes a system command and never returns;use system instead of exec if you want it to return. It fails andreturns false only if the command does not exist and it is executeddirectly instead of via your system's command shell (see below).

  Since it's a common mistake to use exec instead of system, Perlwarns you if exec is called in void context and if there is a followingstatement that isn't die, warn, or exit (if -w is set--butyou always do that, right?). If you really want to follow an execwith some other statement, you can use one of these styles to avoid the warning:

   exec ('foo')   or print STDERR "couldn't exec foo: $!";
   
   { exec ('foo') }; print STDERR "couldn't exec foo: $!";
   

  If there is more than one argument in LIST, or if LIST is an arraywith more than one value, calls execvp(3) with the arguments in LIST.If there is only one scalar argument or an array with one element in it,the argument is checked for shell metacharacters, and if there are any,the entire argument is passed to the system's command shell for parsing(this is /bin/sh -c on Unix platforms, but varies on other platforms).If there are no shell metacharacters in the argument, it is split intowords and passed directly to execvp, which is more efficient.Examples:

   exec '/bin/echo', 'Your arguments are: ', @ARGV;
   
   exec "sort $outfile | uniq";
   

  If you don't really want to execute the first argument, but want to lieto the program you are executing about its own name, you can specifythe program you actually want to run as an "indirect object" (without acomma) in front of the LIST. (This always forces interpretation of theLIST as a multivalued list, even if there is only a single scalar inthe list.) Example:

   $shell = '/bin/csh';
   
   exec $shell '-sh'; # pretend it's a login shell
   

  or, more directly,

   exec {'/bin/csh'} '-sh';  # pretend it's a login shell
   

  When the arguments get executed via the system shell, results aresubject to its quirks and capabilities. See `STRING` in perlopfor details.

  Using an indirect object with exec or system is also moresecure. This usage (which also works fine with system()) forcesinterpretation of the arguments as a multivalued list, even if thelist had just one argument. That way you're safe from the shellexpanding wildcards or splitting up words with whitespace in them.

   @args = ( "echo surprise" );
   
   
   exec @args;   # subject to shell escapes
   
   # if @args == 1
   
   exec { $args[0] } @args;  # safe even with one-arg list
   

  The first version, the one without the indirect object, ran the echoprogram, passing it "surprise" an argument. The second version didn't;it tried to run a program named "echo surprise", didn't find it, and set$? to a non-zero value indicating failure.

  Beginning with v5.6.0, Perl attempts to flush all files opened foroutput before the exec, but this may not be supported on some platforms(see perlport). To be safe, you may need to set $| ($AUTOFLUSHin English) or call the autoflush() method of IO::Handle on anyopen handles to avoid lost output.

  Note that exec will not call your END blocks, nor will it invokeDESTROY methods on your objects.

  Portability issues: exec in perlport.