How do I list the files in a directory?

原文地址：How do I list the files in a directory?

You want a list of all the files, or all the files matching a certain pattern, or with a certain ending, in a directory

The solution

Reading directories is a bit like reading files. First you open the directory, then you read from it and then you close it. You use a directory handle much as you use a file handle.

Step 1: Opening the directory

To open the directory, we use a function called

opendir

. You use this much like the

open

function to open files. In the example below, we open the /tmp directory:

#!/usr/bin/perl
use strict;
use warnings;

my $directory = '/tmp';

opendir (DIR, $directory) or die $!;

Step 2: Reading the directory

To read the files and directories in the directory we use the

readdir

function.

readdir

returns the name of each file or directory in the opened directory in turn when used in scalar context, or a list of the names of all files and directories in that directory when used in list context. This means that we can use

readdir

in a foreach loop (or any other loop construct):

while (my $file = readdir(DIR)) {

print "$file\n";

}

Step 3: Closing the directory

We use the function

closedir

to close the directory once we are finished with it. Like files, the directory will be closed when the program terminates, but sometimes you will need to explicitly close the directory:

closedir(DIR);

Directory Listing

Provided your program has sufficient access to the directory being read,

readdir

will list every file and directory contained in that directory. However, you often will not want all files or directories. For example, it is quite common to exclude all filenames beginning with a period:

#!/usr/bin/perl

use strict;
use warnings;

my $dir = '/tmp';

opendir(DIR, $dir) or die $!;

while (my $file = readdir(DIR)) {

# Use a regular expression to ignore files beginning with a period
next if ($file =~ m/^\./);

print "$file\n";

}

closedir(DIR);
exit 0;

See further down for a more compact way of doing this.

Find the directories

Sometimes you may want to find all the directories in a directory. Remember that

readdir()

gives you the names of the files and directories, not the paths. If you want to test a file using any of the standard file tests, you need to use the full path:

#!/usr/bin/perl

use strict;
use warnings;

my $dir = '/tmp';

opendir(DIR, $dir) or die $!;

while (my $file = readdir(DIR)) {

# A file test to check that it is a directory
# Use -f to test for a file
next unless (-d "$dir/$file");

print "$file\n";

}

closedir(DIR);
exit 0;

Find files ending in...

Quite often you want to find all files ending in a given suffix. For example, you may want to find all files ending in

.txt

:

#!/usr/bin/perl

use strict;
use warnings;

my $dir = '/tmp';

opendir(DIR, $dir) or die $!;

while (my $file = readdir(DIR)) {

# We only want files
next unless (-f "$dir/$file");

# Use a regular expression to find files ending in .txt
next unless ($file =~ m/\.txt$/);

print "$file\n";
}

closedir(DIR);
exit 0;

An advanced example

A more advanced example is to use

grep

to filter out the files you want. The following example (based on a code sample from

perldoc -f readdir

) gets all the files (not directories) beginning with a period from the open directory. The filenames are found in the array

@dots

.

#!/usr/bin/perl

use strict;
use warnings;

my $dir = '/tmp';

opendir(DIR, $dir) or die $!;

my @dots
= grep {
/^\./             # Begins with a period
&& -f "$dir/$_"   # and is a file
} readdir(DIR);

# Loop through the array printing out the filenames
foreach my $file (@dots) {
print "$file\n";
}

closedir(DIR);
exit 0;

File::Find

You can use the File::Find module to recursively search through a directory (or directories). It is best used when you want to perform some operation on each file. See

perldoc File::Find

for more information.

glob

Another way of getting a directory listing - if you're only interested in the current directory and not in any sub-directories - is to use

glob

. You can pass

glob

a pattern (or patterns) to match and it will return any files that match. The example below will list all .pl and .pm files in the current directory:

#!/usr/bin/perl

use strict;
use warnings;

my @files = glob("*.pl *.pm");

foreach my $file (@files) {

print "$file\n";

}

exit 0;

See also

perldoc -f opendir
perldoc -f readdir
perldoc -f closedir
perldoc -f -X
perldoc -f grep
perldoc File::Find
perldoc -f glob
perldoc File::Glob