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Written by Rajesh Kumar
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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
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-A
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Age of file (at script startup) in days since modification.
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-B
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Is it a binary file?
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-C
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Age of file (at script startup) in days since modification.
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-M
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Age of file (at script startup) in days since modification.
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-O
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Is the file owned by the real user ID?
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-R
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Is the file readable by the real user ID or real group?
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-S
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Is the file a socket?
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-T
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Is it a text file?
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-W
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Is the file writable by the real user ID or real group?
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-X
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Is the file executable by the real user ID or real group?
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-b
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Is it a block special file?
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-c
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Is it a character special file?
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-d
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Is the file a directory?
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-e
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Does the file exist?
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-f
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Is it a plain file?
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-g
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Does the file have the setgid bit set?
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-k
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Does the file have the sticky bit set?
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-l
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Is the file a symbolic link?
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-o
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Is the file owned by the effective user ID?
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-p
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Is the file a named pipe?
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-r
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Is the file readable by the effective user or group ID?
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-s
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Returns the size of the file, zero size = empty file.
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-t
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Is the filehandle opened by a TTY (terminal)?
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-u
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Does the file have the setuid bit set?
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-w
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Is the file writable by the effective user or group ID?
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-x
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Is the file executable by the effective user or group ID?
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-z
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Is the file size zero?
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