Checking File Attributes in Perl
I have been using perl for quite some time now. I have also been using the file handling logic in my scripts. However, what I did not know till now is that you can quickly check for certain file properties in perl. Here is an example:
#!/usr/bin/perl
my (@description,$size);
if (-e $file)
{
push @description, ‘binary’ if (-B _);
push @description, ‘a socket’ if (-S _);
push @description, ‘a text file’ if (-T _);
push @description, ‘a block special file’ if (-b _);
push @description, ‘a character special file’ if (-c _);
push @description, ‘a directory’ if (-d _);
push @description, ‘executable’ if (-x _);
push @description, (($size = -s _)) ? “$size bytes” : ‘empty’;
print “$file is “, join(‘, ‘,@description),”\n”;
}
Nice, isn’t it?
Here is the complete list of features that you can check:
| Operator | Description |
| -A | Age of file (at script startup) in days since modification. |
| -B | Is it a binary file? |
| -C | Age of file (at script startup) in days since modification. |
| -M | Age of file (at script startup) in days since modification. |
| -O | Is the file owned by the real user ID? |
| -R | Is the file readable by the real user ID or real group? |
| -S | Is the file a socket? |
| -T | Is it a text file? |
| -W | Is the file writable by the real user ID or real group? |
| -X | Is the file executable by the real user ID or real group? |
| -b | Is it a block special file? |
| -c | Is it a character special file? |
| -d | Is the file a directory? |
| -e | Does the file exist? |
| -f | Is it a plain file? |
| -g | Does the file have the setgid bit set? |
| -k | Does the file have the sticky bit set? |
| -l | Is the file a symbolic link? |
| -o | Is the file owned by the effective user ID? |
| -p | Is the file a named pipe? |
| -r | Is the file readable by the effective user or group ID? |
| -s | Returns the size of the file, zero size = empty file. |
| -t | Is the filehandle opened by a TTY (terminal)? |
| -u | Does the file have the setuid bit set? |
| -w | Is the file writable by the effective user or group ID? |
| -x | Is the file executable by the effective user or group ID? |
| -z | Is the file size zero? |
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