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how to delete file

mauto
User

Jul 19, 2002, 9:45 AM

Post #1 of 17 (1142 views)

how to delete file	Can't Post

I want to check to see if a file exists, if it does then i want to delete it. How can i do this in perl ?

Pro_4
User

Jul 19, 2002, 3:50 PM

Post #2 of 17 (1136 views)

Re: [mauto] how to delete file [In reply to]	Can't Post

this is how i do it...

Code

  
 
if (-e $file) {  
 
unlink($file);  
 
}

Hope that Helps

mauto
User

Jul 22, 2002, 4:53 AM

Post #3 of 17 (1127 views)

Re: [Pro_4] how to delete file [In reply to]	Can't Post

Thanks.

If I've got to delete say 10 files, what would be the best way to achieve this. Can I store them in an array and then delete the lot ?

Jean
User

Jul 22, 2002, 7:30 AM

Post #4 of 17 (1126 views)

Re: [mauto] how to delete file [In reply to]	Can't Post

Sure.

You can do unlink @files;

Another option is to do everything inside a loop:
[perl]my $res;
foreach my $file (@files) {
$res = unlink($file);
print "Failure deleting file $file - $!\n" if $res == 0;
}
# OR
foreach my $file (@files) {
unlink($file) if -e $file;
}[/perl]
In the latter case, you can check unlinking of each file while unlinking an array retuns only the number of successfully deleted files...

Jean Spector
SQA Engineer @ Exanet
jean.spector@softhome.net

There are only 10 types of people in the world -
Those who understand binary, and those who don't.

(This post was edited by Jean on Jul 22, 2002, 7:34 AM)

mauto
User

Jul 22, 2002, 10:33 AM

Post #5 of 17 (1120 views)

Re: [Jean] how to delete file [In reply to]	Can't Post

Thanks.

I have a long list of files. I want to modify your script to read them from a text file and delete them one at a time if they exist.

currently, I have the following:

my $path = 'c:/temp/';

(@files) = ($path . 'file1.txt', $path . 'file2.txt', $path . 'file3.txt', $path . 'file4.txt', $path . 'file5.txt', $path . 'file6.txt', $path . 'file7.txt', $path . 'file8.txt');

foreach my $file (@files) {
unlink($file) if -e $file;
}

Jean
User

Jul 22, 2002, 11:18 PM

Post #6 of 17 (1115 views)

Re: [mauto] how to delete file [In reply to]	Can't Post

The changes you have to make are very slight...

Here is the example:[perl]my $listfile = 'dir/listfile.txt'; # You can omit the 'dir/' part in case the file is located in the same directory as the script
my $res;

open(FILE, $listfile) or die "Error opening file $listfile - $!\n";
while (my $file = <FILE>) { # Read from file line-by-line
chomp $file; # Remove trailing CRLFs
print "Unlinking file $file\n"; # Pring a message to the screen
unlink $file if -e $file; # Delete the file
}
close(FILE);[/perl]

Paul
Enthusiast

Jul 23, 2002, 2:43 AM

Post #7 of 17 (1110 views)

Re: [Jean] how to delete file [In reply to]	Can't Post

>>
unlink $file if -e $file; # Delete the file
<<

You might want to do something with $! otherwise the files may not unlink and you'll never know.

Jean
User

Jul 23, 2002, 4:04 AM

Post #8 of 17 (1108 views)

Re: [RedRum] how to delete file [In reply to]	Can't Post

Mauto:
I agree with [ RedRum ] - it is a really good idea to check whether the file was actually deleted or the function call has failed...

RedRum:
In my first post in this thread I've offered two solutions and one of them used the return value of the unlink() to determine the outcome. Afterwards I've noticed that the thread author chose the solution without error control, thus the last solution Tongue

mauto
User

Jul 23, 2002, 6:36 AM

Post #9 of 17 (1103 views)

Re: [Jean] how to delete file [In reply to]	Can't Post

Thanks for the advice.

Just one final question. I want to put a header in listfile.txt, which will contain data other than filenames. How can I ensure the script reads from the second line and ignores the header ?

Jean
User

Jul 23, 2002, 6:48 AM

Post #10 of 17 (1101 views)

Re: [mauto] how to delete file [In reply to]	Can't Post

Two options:

1. Ignore the first line of the file no matter what - just put the <FILE>; line right after open() call (not very nice, but it does what you need)

2. Ignore ALL lines that begin with the pound sign ('#') - add the next if $file =~ /^\s*#/; as a first line of the while block (much nicer solution) and allows for additional comments. Of course you will have to begin all your comment lines (including the first one) with the pound sign...

mauto
User

Jul 23, 2002, 7:00 AM

Post #11 of 17 (1096 views)

Re: [mauto] how to delete file [In reply to]	Can't Post

Thanks, option 2 works fine.

Can you explain the line: ~ /^\s*#/;
in words please ?

Jean
User

Jul 23, 2002, 8:26 AM

Post #12 of 17 (1095 views)

Re: [mauto] how to delete file [In reply to]	Can't Post

$variable =~ /regex/ means regular expression match (regex is the regular expression itself). The line checks whether the regex matches the contents of the $variable.

Now to the regex:
^ - in the beginning of the regex means the beginning of the line
\s - means whitespace (space, tab etc.)
* - means any number of characters of the previous kind (in our case any number of whitespace - including zero)
# - means #

In other words we match the pound sign in the beginning of the line optionally preceded by any number of whitespace...

If it's not enough, you can look for the regex explanation in the FAQ and there is a regex explanation generator written (if I remember correctly) by [ japhy ]

Jean
User

Jul 23, 2002, 8:37 AM

Post #13 of 17 (1093 views)

Re: [mauto] how to delete file [In reply to]	Can't Post

I've even found the link to the japhy's (it's his all right) OGRE http://japhy.perlmonk.org/YAPE/OGRE.cgi, but for some reson the site's down Unsure

- probably he's moved the OGRE to some other place...

Jean Spector
SQA Engineer @ Exanet
jean.spector@softhome.net

There are only 10 types of people in the world -
Those who understand binary, and those who don't.

Zisu
Novice

Jul 23, 2002, 11:06 PM

Post #14 of 17 (1087 views)

Re: [mauto] how to delete file [In reply to]	Can't Post

I found site: http://www.codebits.com/p5be/ to be very useful. Printed almost whole tutorial there, 400 pages or so. Scroll down and look for "chapters" at the left side. Dunno if its the best, but for a beginner like me it'll be enough for a long time.
- Just another beginner -

davorg
Thaumaturge / Moderator

Jul 29, 2002, 2:45 AM

Post #15 of 17 (1077 views)

Re: [mauto] how to delete file [In reply to]	Can't Post

Assuming that you have your list of files in @files

Code

$del = unlink grep { -e } @files;

$del will contain the number of files delted successfully.

--
Dave Cross, Perl Hacker, Trainer and Writer
http://www.dave.org.uk/
Get more help at Perl Monks

Paul
Enthusiast

Jul 29, 2002, 7:27 AM

Post #16 of 17 (1073 views)

Re: [davorg] how to delete file [In reply to]	Can't Post

>>
$del = unlink grep { -e } @files;
<<

Or perhaps:

$del = unlink grep { -w } @files;

davorg
Thaumaturge / Moderator

Jul 29, 2002, 7:43 AM

Post #17 of 17 (1069 views)

Re: [RedRum] how to delete file [In reply to]	Can't Post

On Unix, a file doesn't need to be writable for you to be able to delete it. You just need write permissions on the directory.

OTOH, a file does need to exist before you can delete it :)

--
Dave Cross, Perl Hacker, Trainer and Writer
http://www.dave.org.uk/
Get more help at Perl Monks

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