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exec not working?

by UVB (Acolyte)
on Jan 30, 2012 at 02:44 UTC ( #950689=perlquestion: print w/replies, xml ) Need Help??
UVB has asked for the wisdom of the Perl Monks concerning the following question:

I recently upgraded my Strawberry perl and my 'runperl.bat' based scripts have stopped working. On further investigation, I find that exec no longer works - the script below will complain about line 4
# Test perl execution system "perl -v"; system "perl", "d:\\src_test\\perl\\"; exec "perl", "d:\\src_test\\perl\\";
Can't exec "perl": Invalid argument at C:\Users\rattrill.EOL\Desktop\t line 4.
What have I done to my installation that is causing the behaviour of exec to change? Any help would be most appreciated.

Update - The problem simply was that my path had grown too long. Removing some of the junk from my %PATH% resolved the problem

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Re: exec not working?
by kielstirling (Scribe) on Jan 30, 2012 at 02:57 UTC

    Seems like the path to Perl has changed or it is not in the PATH ENV

    What happens if you put the full path to Perl?

    Also a quick Google found "Invalid argument" error with exec()

    -Kiel R Stirling
      Adding the full path to perl.exe fixed the problem although perl is on the path environment variable. The behaviour is strange because the earlier lines can find perl fine without prefixing the path. Thanks, Ross.

        Did you close and restart whatever "session" you were running your scripts from following the Perl install and include path change? The session's version of the include path wouldn't be affected by any changes made outside the session or any changes made in child sessions.

        True laziness is hard work
        although perl is on the path environment variable
        How did you verify this? Did you check the environment in exactly that shell in which you were executing the Perl program?

        Did you also check whether ther are maybe TWO files with a name like perl.* in your PATH?

        Ronald Fischer <>
Re: exec not working?
by Anonymous Monk on Jan 30, 2012 at 04:10 UTC

        A real one might look like this

        Notice ...perl.exe and Config{perlpath}

        @rem = '--*-Perl-*-- @echo off if "%OS%" == "Windows_NT" goto WinNT D:\somefullpathto\bin\perl.exe -x -S "%0" %1 %2 %3 %4 %5 %6 %7 %8 %9 goto endofperl :WinNT D:\somefullpathto\bin\perl.exe -x -S %0 %* if NOT "%COMSPEC%" == "%SystemRoot%\system32\cmd.exe" goto endofperl if %errorlevel% == 9009 echo You do not have Perl in your PATH. if errorlevel 1 goto script_failed_so_exit_with_non_zero_val 2>nul goto endofperl @rem '; #!perl #line 15 eval 'exec perl -x -S "$0" ${1+"$@"}' if 0; # In case running under some shell require 5; use Getopt::Std; use Config; $0 =~ s|.*[/\\]||; my $usage = <<EOT; Usage: $0 [-h] or: $0 [-w] [-u] [-a argstring] [-s stripsuffix] [files] or: $0 [-w] [-u] [-n ntargs] [-o otherargs] [-s stripsuffix] [file +s] -n ntargs arguments to invoke perl with in generated fil +e when run from Windows NT. Defaults to '-x -S %0 %*'. -o otherargs arguments to invoke perl with in generated fil +e other than when run from Windows NT. Defa +ults to '-x -S "%0" %1 %2 %3 %4 %5 %6 %7 %8 %9' +. -a argstring arguments to invoke perl with in generated fil +e ignoring operating system (for compatibili +ty with previous pl2bat versions). -u update files that may have already been proces +sed by (some version of) pl2bat. -w include "-w" on the /^#!.*perl/ line (unless a /^#!.*perl/ line was already present). -s stripsuffix strip this suffix from file before appending " +.bat" Not case-sensitive Can be a regex if it begins with '/' Defaults to "/\.plx?/" -h show this help EOT my %OPT = (); warn($usage), exit(0) if !getopts('whun:o:a:s:',\%OPT) or $OPT{'h'}; # NOTE: %0 is already enclosed in doublequotes by cmd.exe, as appropri +ate $OPT{'n'} = '-x -S %0 %*' unless exists $OPT{'n'}; $OPT{'o'} = '-x -S "%0" %1 %2 %3 %4 %5 %6 %7 %8 %9' unless exists $OPT +{'o'}; $OPT{'s'} = '/\\.plx?/' unless exists $OPT{'s'}; $OPT{'s'} = ($OPT{'s'} =~ m#^/([^/]*[^/\$]|)\$?/?$# ? $1 : "\Q$OPT{'s' +}\E"); my $head; if( defined( $OPT{'a'} ) ) { $head = <<EOT; \@rem = '--*-Perl-*-- \@echo off $Config{perlpath} $OPT{'a'} goto endofperl \@rem '; EOT } else { $head = <<EOT; \@rem = '--*-Perl-*-- \@echo off if "%OS%" == "Windows_NT" goto WinNT $Config{perlpath} $OPT{'o'} goto endofperl :WinNT $Config{perlpath} $OPT{'n'} if NOT "%COMSPEC%" == "%SystemRoot%\\system32\\cmd.exe" goto endof +perl if %errorlevel% == 9009 echo You do not have Perl in your PATH. if errorlevel 1 goto script_failed_so_exit_with_non_zero_val 2>nul goto endofperl \@rem '; EOT } $head =~ s/^\t//gm; my $headlines = 2 + ($head =~ tr/\n/\n/); my $tail = "\n__END__\n:endofperl\n"; @ARGV = ('-') unless @ARGV; foreach ( @ARGV ) { process($_); } sub process { my( $file )= @_; my $myhead = $head; my $linedone = 0; my $taildone = 0; my $linenum = 0; my $skiplines = 0; my $line; my $start= $Config{startperl}; $start= "#!perl" unless $start =~ /^#!.*perl/; open( FILE, $file ) or die "$0: Can't open $file: $!"; @file = <FILE>; foreach $line ( @file ) { $linenum++; if ( $line =~ /^:endofperl\b/ ) { if( ! exists $OPT{'u'} ) { warn "$0: $file has already been converted to a batch file!\n" +; return; } $taildone++; } if ( not $linedone and $line =~ /^#!.*perl/ ) { if( exists $OPT{'u'} ) { $skiplines = $linenum - 1; $line .= "#line ".(1+$headlines)."\n"; } else { $line .= "#line ".($linenum+$headlines)."\n"; } $linedone++; } if ( $line =~ /^#\s*line\b/ and $linenum == 2 + $skiplines ) { $line = ""; } } close( FILE ); $file =~ s/$OPT{'s'}$//oi; $file .= '.bat' unless $file =~ /\.bat$/i or $file =~ /^-$/; open( FILE, ">$file" ) or die "Can't open $file: $!"; print FILE $myhead; print FILE $start, ( $OPT{'w'} ? " -w" : "" ), "\n#line ", ($headlines+1), "\n" unless $linedone; print FILE @file[$skiplines..$#file]; print FILE $tail unless $taildone; close( FILE ); } __END__ =head1 NAME pl2bat - wrap perl code into a batch file =head1 SYNOPSIS B<pl2bat> B<-h> B<pl2bat> [B<-w>] S<[B<-a> I<argstring>]> S<[B<-s> I<stripsuffix>]> [f +iles] B<pl2bat> [B<-w>] S<[B<-n> I<ntargs>]> S<[B<-o> I<otherargs>]> S<[B<-s +> I<stripsuffix>]> [files] =head1 DESCRIPTION This utility converts a perl script into a batch file that can be executed on DOS-like operating systems. This is intended to allow you to use a Perl script like regular programs and batch files where you just enter the name of the script [probably minus the extension] plus any command-line arguments and the script is found in your B<PATH +> and run. =head2 ADVANTAGES There are several alternatives to this method of running a Perl script +. They each have disadvantages that help you understand the motivation for using B<pl2bat>. =over =item 1 C:> perl x:/path/to/ [args] =item 2 C:> perl -S [args] =item 3 C:> perl -S script [args] =item 4 C:> ftype Perl=perl.exe "%1" %* C:> assoc .pl=Perl then C:> [args] =item 5 C:> ftype Perl=perl.exe "%1" %* C:> assoc .pl=Perl C:> set PathExt=%PathExt%;.PL then C:> script [args] =back B<1> and B<2> are the most basic invocation methods that should work o +n any system [DOS-like or not]. They require extra typing and require that the script user know that the script is written in Perl. This is a pain when you have lots of scripts, some written in Perl and some not. It can be quite difficult to keep track of which scripts need to be run through Perl and which do not. Even worse, scripts often get rewritten from simple batch files into more powerful Perl scripts in which case these methods would require all existing users of the scrip +ts be updated. B<3> works on modern Win32 versions of Perl. It allows the user to omit the ".pl" or ".bat" file extension, which is a minor improvement. B<4> and B<5> work on some Win32 operating systems with some command shells. One major disadvantage with both is that you can't use them in pipelines nor with file redirection. For example, none of the following will work properly if you used method B<4> or B<5>: C:> <infile C:> >outfile C:> echo y | C:> | more This is due to a Win32 bug which Perl has no control over. This bug is the major motivation for B<pl2bat> [which was originally written for DOS] being used on Win32 systems. Note also that B<5> works on a smaller range of combinations of Win32 systems and command shells while B<4> requires that the user know that the script is a Perl script [because the ".pl" extension must be entered]. This makes it hard to standardize on either of these methods. =head2 DISADVANTAGES There are several potential traps you should be aware of when you use B<pl2bat>. The generated batch file is initially processed as a batch file each time it is run. This means that, to use it from within another batch file you should precede it with C<call> or else the calling batch file will not run any commands after the script: call script [args] Except under Windows NT, if you specify more than 9 arguments to the generated batch file then the 10th and subsequent arguments are silently ignored. Except when using F<CMD.EXE> under Windows NT, if F<perl.exe> is not in your B<PATH>, then trying to run the script will give you a generic "Command not found"-type of error message that will probably make you think that the script itself is not in your B<PATH>. When using F<CMD.EXE> under Windows NT, the generic error message is followed by "You do not have Perl in your PATH", to make this clearer. On most DOS-like operating systems, the only way to exit a batch file is to "fall off the end" of the file. B<pl2bat> implements this by doing C<goto :endofperl> and adding C<__END__> and C<:endofperl> as the last two lines of the generated batch file. This means: =over =item No line of your script should start with a colon. In particular, for this version of B<pl2bat>, C<:endofperl>, C<:WinNT>, and C<:script_failed_so_exit_with_non_zero_val> should not be used. =item Care must be taken when using C<__END__> and the C<DATA> file ha +ndle. One approach is: . #!perl . while( <DATA> ) { . last if /^__END__$/; . [...] . } . __END__ . lines of data . to be processed . __END__ . :endofperl The dots in the first column are only there to prevent F<cmd.exe> to i +nterpret the C<:endofperl> line in this documentation. Otherwise F<pl2bat.bat> + itself wouldn't work. See the previous item. :-) =item The batch file always "succeeds" The following commands illustrate the problem: C:> echo exit(99); > C:> pl2bat C:> perl -e "print system('perl')" 99 C:> perl -e "print system('fail.bat')" 0 So F<fail.bat> always reports that it completed successfully. Actuall +y, under Windows NT, we have: C:> perl -e "print system('fail.bat')" 1 So, for Windows NT, F<fail.bat> fails when the Perl script fails, but the return code is always C<1>, not the return code from the Perl scri +pt. =back =head2 FUNCTION By default, the ".pl" suffix will be stripped before adding a ".bat" s +uffix to the supplied file names. This can be controlled with the C<-s> opt +ion. The default behavior is to have the batch file compare the C<OS> environment variable against C<"Windows_NT">. If they match, it uses the C<%*> construct to refer to all the command line arguments that were given to it, so you'll need to make sure that works on your variant of the command shell. It is known to work in the F<CMD.EXE> s +hell under Windows NT. 4DOS/NT users will want to put a C<ParameterChar = +*> line in their initialization file, or execute C<setdos /p*> in the shell startup file. On Windows95 and other platforms a nine-argument limit is imposed on command-line arguments given to the generated batch file, since they may not support C<%*> in batch files. These can be overridden using the C<-n> and C<-o> options or the deprecated C<-a> option. =head1 OPTIONS =over 8 =item B<-n> I<ntargs> Arguments to invoke perl with in generated batch file when run from Windows NT (or Windows 98, probably). Defaults to S<'-x -S %0 %*'>. =item B<-o> I<otherargs> Arguments to invoke perl with in generated batch file except when run from Windows NT (ie. when run from DOS, Windows 3.1, or Windows 95 +). Defaults to S<'-x -S "%0" %1 %2 %3 %4 %5 %6 %7 %8 %9'>. =item B<-a> I<argstring> Arguments to invoke perl with in generated batch file. Specifying B<-a> prevents the batch file from checking the C<OS> environment variable to determine which operating system it is being run from. =item B<-s> I<stripsuffix> Strip a suffix string from file name before appending a ".bat" suffix. The suffix is not case-sensitive. It can be a regex if it begins with '/' (the trailing '/' is optional and a trailing C<$> is always assumed). Defaults to C</.plx?/>. =item B<-w> If no line matching C</^#!.*perl/> is found in the script, then such a line is inserted just after the new preamble. The exact line depends on C<$Config{startperl}> [see L<Config>]. With the B<-w> option, C<" -w"> is added after the value of C<$Config{startperl}>. If a line matching C</^#!.*perl/> already exists in the script, then it is not changed and the B<-w> option is ignored. =item B<-u> If the script appears to have already been processed by B<pl2bat>, then the script is skipped and not processed unless B<-u> was specified. If B<-u> is specified, the existing preamble is replaced. =item B<-h> Show command line usage. =back =head1 EXAMPLES C:\> pl2bat bar.PM [..creates foo.bat, bar.PM.bat..] C:\> pl2bat -s "/\.pl|\.pm/" bar.PM [..creates foo.bat, bar.bat..] C:\> pl2bat < somefile > another.bat C:\> pl2bat > another.bat print scalar reverse "rekcah lrep rehtona tsuj\n"; ^Z [..another.bat is now a certified japh application..] C:\> ren *.bat *.pl C:\> pl2bat -u *.pl [..updates the wrapping of some previously wrapped scripts..] C:\> pl2bat -u -s .bat *.bat [..same as previous example except more dangerous..] =head1 BUGS C<$0> will contain the full name, including the ".bat" suffix when the generated batch file runs. If you don't like this, see runperl.bat for an alternative way to invoke perl scripts. Default behavior is to invoke Perl with the B<-S> flag, so Perl will search the B<PATH> to find the script. This may have undesirable effects. On really old versions of Win32 Perl, you can't run the script via C:> script.bat [args] and must use C:> script [args] A loop should be used to build up the argument list when not on Windows NT so more than 9 arguments can be processed. See also L</DISADVANTAGES>. =head1 SEE ALSO perl, perlwin32, runperl.bat =cut __END__ :endofperl
Re: exec not working?
by UVB (Acolyte) on May 31, 2013 at 05:08 UTC
    A lot later on - I found out that the problem was simply that my path had grown too long. Trimming junk out of my %PATH% solved the problem. Thank you to everybody who helped me with this.

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Approved by Eliya
[marto]: there are many, to this day.
[ovedpo15]: @Corion Yes I use the regex you showed me. its very good regex. although now i need to know that substring unit that comma
marto mad corrections to one around 18 months ago
[ovedpo15]: my code checks the value after that comma, if it isn't valid it will remove it. so I would like to remove the substring after that comma meaning getting the string before comma.
[hippo]: Are you sure that Text::CSV_XS isn't already installed at your work? It's such a useful module that it might well be there.
[marto]: pointing out the advantages of cpan modules is well worth in, as both developer and $client/$company benefit greatly
[Tux]: $src =~ m{^(.*),(.*)$/ and $2 !~ $valid and $src = $1;
[Tux]: s,/,},

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