Directory or File

Thorbar

I'm writing a perl script at the moment and I have to loop through a file structure and do certain things to the objects in each directory depending on if they're files or directories.

At the moment I've hacked a solution where I do an ls on everything in the directory and depending on what's returned decide if its a file or a directory. IE if you do ls on a file it just returns the file name while if you do a ls on a directory it will return the contents of that directory. This isn't bullet proof tho because if a directory contains only one file which is the same name of its parent directory then you'll think a directory is a file. I was thinking of just using the more command which returns *** <directory name>: directory *** if its a directory and then the contents of the file if its not but if you do a more on an image file it can cause errors.

Are there any Unix commands I can use which will tell me right away whether what my script is looking at is a file or directory? Failing that does anyone have any other suggestions on a different way to go about finding out if something is a file or directory? Any help is appreciated.

niallb

If you're shelling out to run 'ls' anyway,
you could use the 'file' command which is very versatile.

It will return name: directory if it's a directory.

You can also test for it in bash,
as in [ -d name ] will return true if name is a directory.
[ -d name ] && echo IS A DIRECTORY
[ -d name ] !! echo IS NOT A DIRECTORY
whichever suits best.

not 100% on the equivalent perl syntax,
though if you tried to open a file descriptor
on it and it failed, it MIGHT be a directory :-)

ls -l would have given you enough info,
as the attributes would begin with a d.

If you have to loop through a large file structure,
you should take a look at the find command.
It can scan through a directory tree and find for - example - all directories,
and either return a list of them or perform an action on them.
Might suit your script down to the ground.

Best of luck,
Niall B.

davej

No No No!

There are built in perl commands to handle this.

look at the alphabetical list of functions in perldoc perlfunc


if (-d '/notsure') { # -d tests a file to see if it's a directory
print "this is a directory";
}
else {
print "this is not a directory";
}



To get a list of files (including directories) in a directory do this:

opendir (DIR, '/path/to/dir') || die "Couldn't open dir: $!";
@list=grep(!/^\.\.?$/, readdir DIR); # @list now contains filenames


davej

Zaltais

If you're recursing subdirectories

use File::Find;

find (\&dosomething, '/start/directory');


sub dosomething {

#rob davej's example and modify it
if (-d $File::Find::name) { # -d tests a file to see if it's a directory
print "$File::Find::name is a directory\n";
}
elsif (-f $File::Find::name) {
print "$File::Find::name is a file\n";
}

}


There are also checks for special files, text files, files with the executeable bit set, readable files etc, etc, etc....

Read up on File::Find (which is a native perl implementation of the find command suggested by niallb) and as davej said the alpabetical functions.

Perldoc is dead handy.

And cos I'm feeling generous this morning....

Alphabetical functions

File::Find

Probably better suited to programming too.

niallb

Originally posted by davej
No No No!
There are built in perl commands to handle this.

What's with the "No No No" ?
How about 'This is how you'd do it in perl'

Seeing as the script itself is in perl, it's a cleaner way of doing it,
but the QUESTION was
Are there any Unix commands I can use which will tell me right away whether what my script is looking at is a file or directory?

Thorbar

Thanks for all the suggestions lads. Don't know why I didn't think of using the perl built in functions, I've used them in other projects before but on the current project I'm working on I'm just adding new features to an older script and I was sort of doing things the same way the original programmer had. Anyway thanks again for all the links and suggestions.

Barry