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Posted on 2006-11-05
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is there a command line to make sure file exits or not?
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Question by:perlperl
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10 Comments
 

Author Comment

by:perlperl
ID: 17878165
should work for both windows and unix
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Author Comment

by:perlperl
ID: 17878202
i cannot use if(-e $filename)
because sometimes i execute my file on remote host....so i need the command line which can work on both unix and windows
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Expert Comment

by:ozo
ID: 17878392
Why do you think that -e does not work on both unix and windows?
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Expert Comment

by:Tintin
ID: 17878542
If you want to check for the existence of a *file*, you are better off using the -f flag.  -e will be true if $filename is a directory, link, device etc.

if (-f $filename)

is 100% portable/compatible across *all* operating systems that Perl runs on (at that's a big list)
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Expert Comment

by:Tintin
ID: 17878545
Please show us what steps you've used to determine it doesn't work on windows and unix servers?  

Putting my ESP hat on, I'm guessing it's a path issue.
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Author Comment

by:perlperl
ID: 17878578
i know u r correct but u didn't get my question....i know -e works on both....
but i m looking for a command line (and not inside the perl script)
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Assisted Solution

by:ozo
ozo earned 400 total points
ID: 17878591
perl -e "print 'file exists' if -f shift" filename
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Author Comment

by:perlperl
ID: 17878595
Excellent!!!
what does shift does??
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Accepted Solution

by:
Tintin earned 100 total points
ID: 17878676
perldoc -f shift

shift shifts the parameter list.  So in ozo's example, the if test if using the shifted parameter, ie: filename
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Expert Comment

by:Tintin
ID: 17878687
Also the following FAQ is relevant

perldoc -q one-liners
Found in /usr/local/lib/perl5/5.8.5/pod/perlfaq3.pod
     Why don't Perl one-liners work on my DOS/Mac/VMS system?

     The problem is usually that the command interpreters on
     those systems have rather different ideas about quoting than
     the Unix shells under which the one-liners were created.  On
     some systems, you may have to change single-quotes to double
     ones, which you must NOT do on Unix or Plan9 systems.  You
     might also have to change a single % to a %%.

     For example:

         # Unix
         perl -e 'print "Hello world\n"'

         # DOS, etc.
         perl -e "print \"Hello world\n\""

         # Mac
         print "Hello world\n"
          (then Run "Myscript" or Shift-Command-R)

         # MPW
         perl -e 'print "Hello world\n"'

         # VMS
         perl -e "print ""Hello world\n"""

     The problem is that none of these examples are reliable:
     they depend on the command interpreter.  Under Unix, the
     first two often work. Under DOS, it's entirely possible that
     neither works.  If 4DOS was the command shell, you'd
     probably have better luck like this:

       perl -e "print <Ctrl-x>"Hello world\n<Ctrl-x>""

     Under the Mac, it depends which environment you are using.
     The MacPerl shell, or MPW, is much like Unix shells in its
     support for several quoting variants, except that it makes
     free use of the Mac's non-ASCII characters as control
     characters.

     Using qq(), q(), and qx(), instead of "double quotes",
     'single quotes', and `backticks`, may make one-liners easier
     to write.

     There is no general solution to all of this.  It is a mess.
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