Showing posts with label command line. Show all posts
Showing posts with label command line. Show all posts
Saturday 13 October 2012
How To Exclude Directory While Compressing With Tar
Quite a handy and useful tip here. Several times, you want to compress files and folders but there might be cases when you want to compress your data excluding some of the directories. Tar command makes the process easier by providing us a exclusion switch.
I was actually backing up data I had downloaded in the remote server and wanted a copy of backup tar file in my system as well. But all those images that resided in the folders deep inside were not necessary for me. So all I did was something like below:
The above command effectively excludes all the sub directories from testdirectory having the string image (eg. image, images, images_old in my case) and creates the backup.tar file. Moreover, the --exclude switch also co-operates the regular expressions so you can specify the regex to filter the directories. As an example, the command below excludes the directories a, b, c, d, and e while creating the tarball.
You can exploit this switch for ease several times in your daily works. I hope this helps :)
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I was actually backing up data I had downloaded in the remote server and wanted a copy of backup tar file in my system as well. But all those images that resided in the folders deep inside were not necessary for me. So all I did was something like below:
adm@RServ:~$ tar cvf backup.tar test --exclude=image*
The above command effectively excludes all the sub directories from testdirectory having the string image (eg. image, images, images_old in my case) and creates the backup.tar file. Moreover, the --exclude switch also co-operates the regular expressions so you can specify the regex to filter the directories. As an example, the command below excludes the directories a, b, c, d, and e while creating the tarball.
adm@RServ:~$ tar cvf backup.tar test --exclude=[a-e]
You can exploit this switch for ease several times in your daily works. I hope this helps :)
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How To Exclude Directory While Compressing With Tar
2012-10-13T19:32:00+05:45
Cool Samar
command line|linux|tricks and tips|
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Empty Trash From Command Line In Ubuntu
CLI is such a sexy piece so why bother using GUI, even for cleaning up your trash. In this post, you will see how you can empty trash in Ubuntu from command line.
The trash you see in GUI is nothing but just the view for the files deleted by users which are temporarily moved to the special location of user's home directory. For any user, the trash location is ~/.local/share/Trash/. That is, whatever a user deletes gets saved in this location.
I hope this becomes useful :)
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The trash you see in GUI is nothing but just the view for the files deleted by users which are temporarily moved to the special location of user's home directory. For any user, the trash location is ~/.local/share/Trash/. That is, whatever a user deletes gets saved in this location.
samar@samar-Techgaun:~$ rm -rf ~/.local/share/Trash/
I hope this becomes useful :)
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Empty Trash From Command Line In Ubuntu
2012-10-13T16:11:00+05:45
Cool Samar
command line|tricks and tips|ubuntu|ubuntu 11.10|ubuntu 12.04|ubuntu 12.10|
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Add Google Search Support In Gnome-Terminal
Gnome-terminal is my favorite thing in my system and recently I came to know that I could add google search support in gnome-terminal which is totally awesome. Ubuntu Tweak already includes the google search support but if you want google search in your terminal without the whole ubuntu tweak, you can follow this guide.
All you need to do is add the PPA and you can easily install the gnome-terminal with google search support. Fire up the terminal and enter the following commands:
Credits: Ubuntu Tweak
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All you need to do is add the PPA and you can easily install the gnome-terminal with google search support. Fire up the terminal and enter the following commands:
sudo add-apt-repository ppa:tualatrix/personal
sudo apt-get update
sudo apt-get install gnome-terminal
sudo apt-get update
sudo apt-get install gnome-terminal
Credits: Ubuntu Tweak
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Add Google Search Support In Gnome-Terminal
2012-10-13T09:22:00+05:45
Cool Samar
command line|tricks and tips|ubuntu|
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Tuesday 2 October 2012
Binary, Hex, Octal and Decimal Conversion Under Linux
Base conversions are easy with linux CLI. No need of fancy GUI-based calculator to perform base conversions when there is our favorite linux terminal.
We will be using bc, a calculator language that supports arbitrary precision numbers with interactive execution of statements. We will exploit the pipelining feature of shell and will let the bc process our query to convert the numbers from one base to other.
As seen in all the examples above, the conversion to decimal numbers does not require you to specify the obase as obase defaults to decimal. The same thing applies for ibase i.e. ibase defaults to decimal base by default as seen in the examples below.
Now lets try some conversion with decimal numbers as the input base.
Below are few more examples of base conversions to clarify the use of the command.
I hope this is helpful ;-)
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We will be using bc, a calculator language that supports arbitrary precision numbers with interactive execution of statements. We will exploit the pipelining feature of shell and will let the bc process our query to convert the numbers from one base to other.
From binary to decimal
The syntax is obvious and we will follow the similar syntax for all the conversions. In this first example, we are converting the binary number 1101101 from input base binary to decimal(obase defaults to decimal unless specified).
samar@samar-Techgaun:~$ echo "ibase=2;1101101" | bc
109
109
From octal to decimal
samar@samar-Techgaun:~$ echo "ibase=8;1101101" | bc
295489
295489
From Hexadecimal to decimal
samar@samar-Techgaun:~$ echo "ibase=16;A1F3DF" | bc
10613727
10613727
From N-base to decimal
All you need to do is provide the appropriate ibase value (eg. ibase=4 for 4-base to decimal conversion).
samar@samar-Techgaun:~$ echo "ibase=16;A1F3DF" | bc
10613727
10613727
As seen in all the examples above, the conversion to decimal numbers does not require you to specify the obase as obase defaults to decimal. The same thing applies for ibase i.e. ibase defaults to decimal base by default as seen in the examples below.
Now lets try some conversion with decimal numbers as the input base.
From decimal to binary
samar@samar-Techgaun:~$ echo "obase=2;109" | bc
1101101
1101101
From decimal to octal
samar@samar-Techgaun:~$ echo "obase=8;295489" | bc
1101101
1101101
From decimal to hexadecimal
samar@samar-Techgaun:~$ echo "obase=16;10613727" | bc
A1F3DF
A1F3DF
From decimal to N-base
All you need to do is provide the appropriate obase value (eg. obase=4 for decimal to 4-base conversion).
samar@samar-Techgaun:~$ echo "obase=4;121" | bc
1321
1321
Below are few more examples of base conversions to clarify the use of the command.
From binary to octal
samar@samar-Techgaun:~$ echo "ibase=2;obase=8;1111" | bc
17
17
From hexadecimal to binary
samar@samar-Techgaun:~$ echo "ibase=16;obase=2;AFBE" | bc
1010111110111110
1010111110111110
I hope this is helpful ;-)
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Binary, Hex, Octal and Decimal Conversion Under Linux
2012-10-02T22:12:00+05:45
Cool Samar
command line|linux|mathematics|tricks and tips|ubuntu|
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Friday 14 September 2012
How To Find The Location Of Command In Linux
Sometimes you need to find the pathnames or locations of commands you use frequently. In this post, I am going to discuss two useful commands that are useful for locating Linux commands.
The first command to locate the Linux commands is which. This command returns the pathnames of the files or links. However, it does not follow the symbolic links.
You can also find the pathnames of multiple commands at once using which command.
The other command is type command which is useful to determine if a command is an alias, a built-in command or an independent command.
You can play more with the type command. I hope this helps :)
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The first command to locate the Linux commands is which. This command returns the pathnames of the files or links. However, it does not follow the symbolic links.
samar@Techgaun:~$ which bash
/bin/bash
/bin/bash
You can also find the pathnames of multiple commands at once using which command.
samar@Techgaun:~$ which -a bash cat ls iftop
/bin/bash
/bin/cat
/bin/ls
/usr/sbin/iftop
/bin/bash
/bin/cat
/bin/ls
/usr/sbin/iftop
The other command is type command which is useful to determine if a command is an alias, a built-in command or an independent command.
samar@Techgaun:~$ type gedit
gedit is /usr/bin/gedit
samar@Techgaun:~$ type grep
grep is aliased to `grep --color=auto'
samar@Techgaun:~$ type -t iftop
file
gedit is /usr/bin/gedit
samar@Techgaun:~$ type grep
grep is aliased to `grep --color=auto'
samar@Techgaun:~$ type -t iftop
file
You can play more with the type command. I hope this helps :)
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How To Find The Location Of Command In Linux
2012-09-14T01:05:00+05:45
Cool Samar
command line|linux|ubuntu|
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Monday 3 September 2012
Preventing Accidental Overwriting Of Files In Bash Shell
How many times has this happened to you? It used to happen once in a while with me. A Linux user learns to use the redirection operators such as '>' and '>>' but accidental overwriting starts to become common in commands you use and shell scripts you write.
The accidental overwriting of files that happens unintentionally is known as clobbering and it commonly happens while using the '>' redirection operator.
In the above example, the mycmd clobbers any existing data in the myfile file if that file exists already. Worse things may happen sometime. Imagine accidentally typing
instead of possibly using other redirection operators (like >> or <). Thankfully, you could recover /etc/passwd from either /etc/passwd- or /var/backups/passwd.bak if you hadn't rm'd these files.
To prevent such accidental overwriting, we can set the noclobber environment variable. Below is a session of enabling this variable:
As seen above, you have to turn on the noclobber variable using the set -o noclobber command in your shell. However, you might want to intentionally overwrite contents of certain files even when the noclobber is turned on.
Notice the >| in place of your normal > redirection operator. Using this operator, you can however overwrite the existing files even if the noclobber is turned on.
If you want to turn off the noclobber variable, type the following:
You can also permanently turn on the noclobber by the following command:
Moreover, such accidental overwriting can be prevented by enabling the interactive mode which is available in most of the linux commands. For example, you can write the alias for many commands that are likely to cause accidental overwriting. See some examples of aliases below:
You could even keep these aliases in your ~/.bashrc file permanently. Enabling such interactive modes by default in the commands that are more likely to cause accidental overwriting can prevent clobbering in many cases.
I hope this proves useful to you :)
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The accidental overwriting of files that happens unintentionally is known as clobbering and it commonly happens while using the '>' redirection operator.
samar@Techgaun:~$ mycmd > myfile
In the above example, the mycmd clobbers any existing data in the myfile file if that file exists already. Worse things may happen sometime. Imagine accidentally typing
samar@Techgaun:~$ mycmd > /etc/passwd
instead of possibly using other redirection operators (like >> or <). Thankfully, you could recover /etc/passwd from either /etc/passwd- or /var/backups/passwd.bak if you hadn't rm'd these files.
To prevent such accidental overwriting, we can set the noclobber environment variable. Below is a session of enabling this variable:
samar@Techgaun:~/Desktop/test$ echo "www.techgaun.com" > myfile
samar@Techgaun:~/Desktop/test$ echo "Overwriting techgaun.com" > myfile
samar@Techgaun:~/Desktop/test$ set -o noclobber
samar@Techgaun:~/Desktop/test$ echo "Retrying to overwrite" > myfile
-bash: myfile: cannot overwrite existing file
samar@Techgaun:~/Desktop/test$ echo "Overwriting techgaun.com" > myfile
samar@Techgaun:~/Desktop/test$ set -o noclobber
samar@Techgaun:~/Desktop/test$ echo "Retrying to overwrite" > myfile
-bash: myfile: cannot overwrite existing file
As seen above, you have to turn on the noclobber variable using the set -o noclobber command in your shell. However, you might want to intentionally overwrite contents of certain files even when the noclobber is turned on.
samar@Techgaun:~$ mycmd >| myfile
Notice the >| in place of your normal > redirection operator. Using this operator, you can however overwrite the existing files even if the noclobber is turned on.
If you want to turn off the noclobber variable, type the following:
samar@Techgaun:~$ set +o noclobber
You can also permanently turn on the noclobber by the following command:
samar@Techgaun:~$ echo "set -o noclobber" >> ~/.bashrc
Moreover, such accidental overwriting can be prevented by enabling the interactive mode which is available in most of the linux commands. For example, you can write the alias for many commands that are likely to cause accidental overwriting. See some examples of aliases below:
samar@Techgaun:~$ alias rm=rm -i
samar@Techgaun:~$ alias mv=mv -i
samar@Techgaun:~$ alias mv=mv -i
You could even keep these aliases in your ~/.bashrc file permanently. Enabling such interactive modes by default in the commands that are more likely to cause accidental overwriting can prevent clobbering in many cases.
I hope this proves useful to you :)
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Preventing Accidental Overwriting Of Files In Bash Shell
2012-09-03T22:56:00+05:45
Cool Samar
bash|command line|fedora|filesystem|linux|ubuntu|ubuntu 11.10|
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Sunday 2 September 2012
How To Search Manual Pages In Linux
Linux system consists of hundreds of binaries, several syscalls, and other stuffs that do have manual page. What if you want to locate or find the commands by searching through the manual pages? In this post, I am going to talk about one such useful command to search through the manual page names and short descriptions.
The command I am talking about is the apropos command. The best way to learn any linux command is to read its corresponding manual and go through the help (-h or --help) so lets poke through the help of apropos itself.
Particularly, the -e switch is quite useful to filter out your search. See the example below:
Each command has its associated short description and the apropos command searches the short description section of appropriate manual page for the provided keyword. You can also specify the search keywords in the form of regular expression for more flexibility. I hope this command counts as useful one :)
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The command I am talking about is the apropos command. The best way to learn any linux command is to read its corresponding manual and go through the help (-h or --help) so lets poke through the help of apropos itself.
samar@Techgaun:~$ apropos -h Usage: apropos [OPTION...] KEYWORD... -d, --debug emit debugging messages -v, --verbose print verbose warning messages -e, --exact search each keyword for exact match -r, --regex interpret each keyword as a regex -w, --wildcard the keyword(s) contain wildcards -a, --and require all keywords to match -l, --long do not trim output to terminal width -C, --config-file=FILE use this user configuration file -L, --locale=LOCALE define the locale for this search -m, --systems=SYSTEM use manual pages from other systems -M, --manpath=PATH set search path for manual pages to PATH -s, --section=SECTION search only this section -?, --help give this help list --usage give a short usage message -V, --version print program version Mandatory or optional arguments to long options are also mandatory or optional for any corresponding short options. The --regex option is enabled by default. Report bugs to cjwatson@debian.org.
Particularly, the -e switch is quite useful to filter out your search. See the example below:
samar@Techgaun:~$ apropos -e tar bf_tar (1) - shell script to write a tar file of a bogofilter direc... bf_tar-bdb (1) - shell script to write a tar file of a bogofilter direc... git-tar-tree (1) - Create a tar archive of the files in the named tree ob... lz (1) - gunzips and shows a listing of a gzip'd tar'd archive mxtar (1) - Wrapper for using GNU tar directly from a floppy disk ptar (1) - a tar-like program written in perl tar (1) - The GNU version of the tar archiving utility tar (5) - format of tape archive files tgz (1) - makes a gzip'd tar archive uz (1) - gunzips and extracts a gzip'd tar'd archive
Each command has its associated short description and the apropos command searches the short description section of appropriate manual page for the provided keyword. You can also specify the search keywords in the form of regular expression for more flexibility. I hope this command counts as useful one :)
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How To Search Manual Pages In Linux
2012-09-02T02:07:00+05:45
Cool Samar
command line|edubuntu|fedora|linux|tricks and tips|ubuntu|
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Friday 27 July 2012
Determine Your SATA Disk Model And Vendor In Ubuntu
Sometimes you need to determine the model and vendor of your hard disk and here is the small tips on how to find those information.
All you have to do is type one of the following commands for the respective outputs:
I hope this becomes useful sometimes. :)
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All you have to do is type one of the following commands for the respective outputs:
cat /sys/class/block/sda/device/model
cat /sys/class/block/sda/device/vendor
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Determine Your SATA Disk Model And Vendor In Ubuntu
2012-07-27T21:36:00+05:45
Cool Samar
command line|linux|ubuntu|
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