File Processing
Changing File Names
In this lesson the student will learn to:
- Open a directory.
- Search a directory.
- Change the names of files using the rename function
By the end of this lesson the student will be able to:
Write a short Perl script which displays the
files in a directory and allows the user to
change the name of a file.
Changing File Names
the following example lists the contents of the current directory and
alters the names of all the files contained in that directory which match a
specified pattern by incrementing the numerical portion of their name by
one.
<![CDATA[
#!/usr/bin/perl -w
my @files = ();
my $folder = ".";
unless(opendir(FOLDER, $folder)){
print "Cannot open folder $folder!\n";
exit;
}
@files = readdir(FOLDER);
closedir(FOLDER);
foreach $item ( reverse sort @files){ #reversing the file names is important!
if( $item =~ m/lib.*/ ){
$new_name = $item;
chomp($new_name);
$new_name =~ s/lib(\d\d).html/$1+1/ge; #increment name by one
if($new_name<10) {
$new_name = "lib0$new_name.html";
}
else{
$new_name = "lib$new_name.html";
}
print "$item --> $new_name\n";
#if file names not reversed the following line
#will fail before reaching the rename function
-e $new_name || rename($item,$new_name);
}
}
exit;
]]>
Here's an example that changes dashes to underscores:
<![CDATA[
#!/usr/bin/perl -w
my @files = ();
my $folder = ".";
unless(opendir(FOLDER, $folder)){
print "Cannot open folder $folder!\n";
exit;
}
@files = readdir(FOLDER);
closedir(FOLDER);
foreach $item ( sort @files){
if( $item =~ m/.*.png/ ) {
$new_name = $item;
chomp($new_name);
$new_name =~ s/(.*)\-(.*)/$1_$2/g;
print "$item --> $new_name\n";
#if file names not reversed the following line
#will fail before reaching the rename function
-e $new_name || rename($item,$new_name);
}
}
exit;
]]>
Here's another example which changes uppercase letters to lowercase:
<![CDATA[
#!/usr/bin/perl -w
my @files = ();
my $folder = ".";
unless(opendir(FOLDER, $folder)){
print "Cannot open folder $folder!\n";
exit;
}
@files = readdir(FOLDER);
closedir(FOLDER);
foreach $item ( sort @files){
if( $item =~ m/.*.png/ ) {
$new_name = $item;
chomp($new_name);
$new_name =~ tr/A-Z/a-z/;
print "$item --> $new_name\n";
rename($item,$new_name);
}
}
exit;
]]>
Perform the following steps to properly test this script:
Create a test directory by typing mkdir TESTDIR and change
directories into TESTDIR by typing cd TESTDIR.
Create several empty files using the touch command like
this:
<![CDATA[
touch lib01.html
touch lib05.html
touch lib09.html
]]>
Get the script up and running and run it several times. After each
execution of the script check the names of the files by typing ls
-l.
ASSIGNMENT:
Write a script which does the following:
- Prints the names of the files in a directory
- Prompts the user to identify a filename to change by typing its name
- Prompts the user to enter a new name for the file
- Does not allow the user to change the name to a name which is already in
the directory