Determining Bits of CPU and OS (32/64-bits)

In order to determine whether OS/CPU is 32-bit or 64-bit,
you can use this shell script.

#!/bin/bash
echo -n "Running "

RES=`uname -a | grep 64`
if [ $? -eq 0 ]; then

    echo -n "64-bit "
else
    echo -n "32-bit "
fi
echo -n "operating system on a "

RES=`cat /proc/cpuinfo | grep " lm "`
if [ $? -eq 0 ]; then

    echo -n "64-bit "
else
    echo -n "32-bit "
fi
echo "machine"

Sample Run:

$ ./os_cpu.sh
Running 64-bit operating system on a 64-bit machine

Let Linux Speak Time and Day for You

I have written a single line command that tells time of the day:

$ espeak "Time is `/bin/date \"+%H
hours %M minutes %S seconds\"`"



You need not to type this command every time, just run the

following commands only one time:


$ echo "alias speak_time='espeak \"Time is \`/bin/date \"+%H hours %M minutes %S seconds\"\`\"'" >> ~/.bashrc

$ source ~/.bashrc



Now, you will be able to run speak_time any number of time at any time, and you will get exact time. :-)


$ speak_time



PS: Requirement of above command is "espeak"


$ sudo apt-get install espeak


For speaking day, just add following alias in your .bashrc file

alias speak_day='espeak "Today is `/bin/date \"+%A, %d %B 20%y\"`"'

Mount Windows Shared Folder onto Linux Directory

Suppose you want to mount Windows shared folder (say shared_folder) on windows machine (IP address 10.226.194.169) on a folder (say /local/smbshare/shared_folder), you just need to give following
command:


$ sudo mount -t smbfs -o username=domainname\\yourname,password=yoursecretpassword -o gid=users,dmask=777,fmask=777,rw //10.226.194.169/shared_folder /local/smbshare/shared_folder

You can verify whether the above command is successful or not, by using:
$ mount | grep shared_folder

If the above command shows some output, it means mount is successful :)

Mounted Filesystem Information

For getting information of a partition (filesystem) which is mounted on a directory on Linux System, I have created a C program. Its listing is given as below:

/*
 * =====================================================================================
 *
 *       Filename:  file_system_stat.c
 *
 *    Description:  Get file system statistics of mounted partition
 *
 *        Version:  1.0
 *        Created:  Thursday 09 July 2009 10:48:02  IST IST
 *       Revision:  none
 *       Compiler:  gcc
 *
 *         Author:  Mitesh Singh Jat (mitesh)
 *
 * =====================================================================================
 */

#include <stdio.h>
#include <sys/statfs.h>

int file_system_stats(const char *pathp)
{
    struct statfs sfs;
    int retval;
    if (pathp == NULL)
    {
        fprintf(stderr, "file_system_stats: cannot find stats of NULL path\n");
        return (-1);
    }
    retval = statfs(pathp, &sfs);
    if (retval < 0)
    {
        fprintf(stderr, "file_system_stats: cannot find file system\n");
        fprintf(stderr, "    stats of partition %s\n", pathp);
        return (-1);
    }
    printf("\n=== Filesystem Stats of '%s' ===\n", pathp);
    printf("Optimal Transfer Block Size = %ld\n", sfs.f_bsize);
    printf("Total data blocks           = %ld\n", sfs.f_blocks);
    printf("Total free data blocks      = %ld\n", sfs.f_bfree);
    printf("Total file nodes            = %ld\n", sfs.f_files);
    printf("Total free file nodes       = %ld\n", sfs.f_ffree);
    printf("=================================================\n\n");
    return (retval);
}

int main(int argc, char *argv[])
{
    int i;
    int retval = 0;
    if (argc <= 1)
    {
        fprintf(stderr, "Usage: %s <path> [more_paths...]\n", argv[0]);
        retval = file_system_stats("./");
        return (retval);
    }

    for (i = 1; i < argc && retval >= 0; ++i)
    {
        retval = file_system_stats(argv[i]);
    }
    return (retval);
}

Compilation:
$ gcc -Wall -o file_system_stat file_system_stat.c

Sample Runs:
--(mitesh@roundduck-lm)-(~/Programming/C/Usp)--
--(0 : 505)$ ./file_system_stat
Usage: ./file_system_stat <path> [more_paths...]

=== Filesystem Stats of './' ===
Optimal Transfer Block Size = 4096
Total data blocks = 9690330
Total free data blocks = 3956097
Total file nodes = 2449408
Total free file nodes = 2315870
=================================================

--(mitesh@roundduck-lm)-(~/Programming/C/Usp)--
--(0 : 506)$ ./file_system_stat /boot

=== Filesystem Stats of '/boot' ===
Optimal Transfer Block Size = 4096
Total data blocks = 12017122
Total free data blocks = 5616343
Total file nodes = 3055616
Total free file nodes = 2830533
=================================================

--(mitesh@roundduck-lm)-(~/Programming/C/Usp)--
--(0 : 507)$ ./file_system_stat /boot /mnt/extra

=== Filesystem Stats of '/boot' ===
Optimal Transfer Block Size = 4096
Total data blocks = 12017122
Total free data blocks = 5616343
Total file nodes = 3055616
Total free file nodes = 2830533
=================================================


=== Filesystem Stats of '/mnt/extra' ===
Optimal Transfer Block Size = 4096
Total data blocks = 21235766
Total free data blocks = 7269970
Total file nodes = 5357568
Total free file nodes = 5357279
=================================================

--(mitesh@roundduck-lm)-(~/Programming/C/Usp)--
--(1 : 508)$ ./file_system_stat /this_is_not_a_partition
file_system_stats: cannot find file system
stats of partition /this_is_not_a_partition





Note: By the way, the block size of a filesystem can be found using commands given at here or here.

Removing Files With Unusual Characters

Suppose, some one (miscreant) got access to your computer and
creates files, which you may not be able to delete or you will end
up deleting all the files/subdirectories of the directory on which
these files are created.

Some examples of such dangerous file names are:
$ ls -l
total 0K
-rw-r--r-- 1 mitesh users 0 2009-07-01 19:19 *
-rw-r--r-- 1 mitesh users 0 2009-07-01 19:20 -rf *
-rw-r--r-- 1 mitesh users 0 2009-07-01 19:27 -rw-r--r--
-rw-r--r-- 1 mitesh users 0 2009-07-01 19:19 test

Now, how are you going to delete above files?

(1) * : If one tries
$ rm *
or
$ rm -r *
This will delete all the files(& all subdirectories) in present working
directory.
Solution:
$ rm -f ./'*'
We can verify this.
$ ls -l
total 0K
-rw-r--r-- 1 mitesh users 0 2009-07-01 19:20 -rf *
-rw-r--r-- 1 mitesh users 0 2009-07-01 19:27 -rw-r--r--
-rw-r--r-- 1 mitesh users 0 2009-07-01 19:19 test

(2) -rf *: If one tries
$ rm -rf *
This will delete all the files & all subdirectories in present working
directory.
Solution:
$ rm -f ./'*'
We can verify this.
$ ls -l
total 0K
-rw-r--r-- 1 mitesh users 0 2009-07-01 19:27 -rw-r--r--
-rw-r--r-- 1 mitesh users 0 2009-07-01 19:19 test

(3) -rw-r--r--: If one tries
$ rm -rw-r--r--
rm: invalid option -- w
Try `rm ./-rw-r--r--' to remove the file `-rw-r--r--'.
Try `rm --help' for more information.
Solution:
$ rm ./-rw-r--r--
Other Solution
$ rm -- -rw-r--r--

Note: So we need to be vigilant, while using 'rm' command.

Finding Block Size of Filesystem

In order to, find block size of a filesystem on Linux,

$ sudo tune2fs -l /dev/sda1 | grep -i 'block size'
Block size: 4096

OR

$ echo "mitesh"> test && du test | awk '{print $1}' && rm -f test
4K

Editing Very Very Large File

Suppose we want to do changes in few lines in a very very large file. It is not possible to open such a big file(say size in GBs > RAM+Swap size) in a editor. Even sed/awk takes very long time, because they do pattern matching if mentioned on every line, otherwise, we can do one line editing with a line number. I have written a Perl Script to edit multiple lines independently. It uses sed commands to edit a line.

Format of Config file is:
line_number:sed_command

#!/usr/bin/perl -w
#===============================================================================
#
#         FILE:  ed_large_file.pl
#
#        USAGE:  ./ed_large_file.pl <config_file> <file_name> [overwrite}
#
#  DESCRIPTION:  Edit very[ very] large file
#
#      OPTIONS:  ---
# REQUIREMENTS:  ---
#         BUGS:  ---
#        NOTES:  ---
#       AUTHOR:  Mitesh Singh Jat (mitesh), <mitesh[at]yahoo-inc[dot]com>
#      VERSION:  1.0
#      CREATED:  Thursday 25 June 2009 02:32:37  IST IST
#     REVISION:  ---
#===============================================================================

use strict;
use warnings;

if (@ARGV < 2)
{
    print STDERR "$0: <config_file> <file_name> [overwrite]\n";
    print STDERR "!!!Be careful while using [overwrite] option,\n";
    print STDERR "because original file will be deleted.\n";
    exit(-1);
}

my $conf_file = $ARGV[0];
my $large_file = $ARGV[1];
my $overwrite = 0;
if (@ARGV >= 3 && $ARGV[2] eq "overwrite")
{
    $overwrite = 1;
}

my $temp_file = `dirname $large_file`;
chomp($temp_file);
if ($temp_file eq "" || (!(-d $temp_file)))
{
    print STDERR "$0: Cannot find dirname for temporary file.\n";
    print STDERR "Please check path of file '$large_file'\n";
    exit(-1);
}

$temp_file = $temp_file . "/temp";
print "Temporary file is '$temp_file'\n";

## Read config file
print "Reading config file '$conf_file'\n";
open(CFH, "$conf_file") or die("Cannot read Config file '$conf_file'\n");
my $line;
my %lineno_sedcmd;
while ($line = <CFH>)
{
    chomp($line);
    my ($lineno, $sedcmd) = split /:/, $line, 2;
    if (defined($sedcmd))
    {
        $lineno_sedcmd{$lineno} = $sedcmd;
        print "$lineno  $lineno_sedcmd{$lineno}\n";
        # Verifying sedcmd before running it;
        # it gives a chance to reedit config file
        my $cmd = "echo \"Mitesh Singh Jat\" | sed '$sedcmd' 1> /dev/null 2>&1";
        if (!(system($cmd) == 0))
        {
            print STDERR "$0: sed command '$sedcmd' for line '$lineno'";
            print STDERR "is having error. Please recheck with \$ man sed\n";
            close(CFH);
            exit(-1);
        }
    }
}
close(CFH);

my @line_nos;
foreach (sort keys (%lineno_sedcmd))
{
    push(@line_nos, $_);
}

## Open large file
open(LFH, "$large_file") or die("$0: Cannot open file '$large_file'");
## Temporary File 
open(OFH, ">$temp_file") or die("$0: Cannot create temporary file '$temp_file'");
my $nline = 0;
my $i = 0;
my $end_idx = @line_nos - 1;
print "Processing...";
while ($line = <LFH>)
{
    ++$nline;
    if ($line_nos[$i] == $nline)       # now edit
    {
        ++$i;   # This config line is over
        if ($i > $end_idx)
        {
            $i = $end_idx;
        }
        chomp($line);
        my $cmd = "echo \"$line\" | sed '$lineno_sedcmd{$nline}'";
        #print "$cmd\n";
        my $out_line = `$cmd`;
        print OFH "$out_line";
        print " $nline"; #sleep 1; # to see progress :)
    }
    else
    {
        print OFH "$line";
    }
}

print "\n";

close(OFH);
close(LFH);

if ($overwrite == 0)
{
    print "done\n";
    exit(0);
}

## Overwite original file by deleting it and moving temp
print "Overwriting...\n";
my $cmd = "rm -f $large_file \&\& mv $temp_file $large_file";
print "$cmd\n";
system($cmd) == 0 
    or die("Problem in overwriting. '$cmd' failed: $?\n");
print "done\n";    
exit(0);

Sample Run:


--(0 : 618)> ./ed_large_file.pl
./ed_large_file.pl: <config_file> <file_name> [overwrite]
!!!Be careful while using [overwrite] option,
because original file will be deleted.
--(mitesh@roundduck-lm)-(~/Programming/Perl/Editing_Large_Files)--
--(255 : 619)> cat large_file.txt
Shree Ganeshay Namah
Shri Bharat Singh Jat
Smt Amita Jat
Mitesh Jat
Shikha Jat
Shilpa Jat
This is garbage line. Please delete it.
--(mitesh@roundduck-lm)-(~/Programming/Perl/Editing_Large_Files)--
--(0 : 620)> cat large_file.conf
1:s/^.*$/!!&!!/
4:s/ / Singh /
7:/.*/d
--(mitesh@roundduck-lm)-(~/Programming/Perl/Editing_Large_Files)--
--(0 : 621)> ./ed_large_file.pl large_file.conf large_file.txt
Temporary file is './temp'
Reading config file 'large_file.conf'
1 s/^.*$/!!&!!/
4 s/ / Singh /
7 /.*/d
Processing... 1 4 7
done
--(mitesh@roundduck-lm)-(~/Programming/Perl/Editing_Large_Files)--
--(0 : 622)> cat ./temp
!!Shree Ganeshay Namah!!
Shri Bharat Singh Jat
Smt Amita Jat
Mitesh Singh Jat
Shikha Jat
Shilpa Jat
--(mitesh@roundduck-lm)-(~/Programming/Perl/Editing_Large_Files)--
--(0 : 623)> ./ed_large_file.pl large_file.conf large_file.txt overwrite
Temporary file is './temp'
Reading config file 'large_file.conf'
1 s/^.*$/!!&!!/
4 s/ / Singh /
7 /.*/d
Processing... 1 4 7
Overwriting...
rm -f large_file.txt && mv ./temp large_file.txt
done
--(mitesh@roundduck-lm)-(~/Programming/Perl/Editing_Large_Files)--
--(0 : 624)> cat large_file.txt
!!Shree Ganeshay Namah!!
Shri Bharat Singh Jat
Smt Amita Jat
Mitesh Singh Jat
Shikha Jat
Shilpa Jat
--(mitesh@roundduck-lm)-(~/Programming/Perl/Editing_Large_Files)--
--(0 : 625)>