Friday, 5 August 2011

find the size of the largest file in current directory

#!usr/bin/perl

opendir(DIR,"./");
my @files = grep { -f $_ } readdir(DIR);
print "@files\n";
my $maxsize=0;
foreach my $file (@files)
{
$maxsize = (stat($file))[7] if (-s $file > $maxsize);
}
print "$maxsize\n";

Little info about stat function : ( perldoc -f stat from unix command line)

stat FILEHANDLE
stat EXPR
stat Returns a 13-element list giving the status info for a file, either the file opened via FILEHANDLE, or named by EXPR. If EXPR is omitted,
it stats $_. Returns a null list if the stat fails. Typically used as follows:

($dev,$ino,$mode,$nlink,$uid,$gid,$rdev,$size,
$atime,$mtime,$ctime,$blksize,$blocks)
= stat($filename);

Not all fields are supported on all filesystem types. Here are the meanings of the fields:

0 dev device number of filesystem
1 ino inode number
2 mode file mode (type and permissions)
3 nlink number of (hard) links to the file
4 uid numeric user ID of fileâs owner
5 gid numeric group ID of fileâs owner
6 rdev the device identifier (special files only)
7 size total size of file, in bytes
8 atime last access time in seconds since the epoch
9 mtime last modify time in seconds since the epoch
10 ctime inode change time in seconds since the epoch (*)
11 blksize preferred block size for file system I/O
12 blocks actual number of blocks allocated

(The epoch was at 00:00 January 1, 1970 GMT.)

(*) The ctime field is non-portable. In particular, you cannot expect it to be a "creation time", see "Files and Filesystems" in perlport
for details.

If "stat" is passed the special filehandle consisting of an underline, no stat is done, but the current contents of the stat structure
from the last "stat", "lstat", or filetest are returned. Example:

if (-x $file && (($d) = stat(_)) && $d < 0) {
print "$file is executable NFS file\n";
}

(This works on machines only for which the device number is negative under NFS.)

Because the mode contains both the file type and its permissions, you should mask off the file type portion and (s)printf using a "%o" if
you want to see the real permissions.

$mode = (stat($filename))[2];
printf "Permissions are %04o\n", $mode & 07777;

In scalar context, "stat" returns a boolean value indicating success or failure, and, if successful, sets the information associated with
the special filehandle "_".

The File::stat module provides a convenient, by-name access mechanism:

use File::stat;
$sb = stat($filename);
printf "File is %s, size is %s, perm %04o, mtime %s\n",
$filename, $sb->size, $sb->mode & 07777,
scalar localtime $sb->mtime;
continued...............

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