Author Archives: vishnupalakkal

About vishnupalakkal

Research Scholar

Useful HTML code Snippets created using “Manage Snippets” plugin for GEdit text editor

When it comes to writing a post using html editor, you will be having some frequently used codes to do some tasks. Life will be easier, if you have some shortcut key or other faster way (like writing a shortcode and press “tab” key) to insert these frequently used codes. There comes the use of “Snippets”.

You can use a text editor like GEdit for typing html codes in a faster way, if you have “Manage Snippets” plugin.

Some useful HTML code Snippets are created using “Manage Snippets” plugin for GEdit text editor. These snippets are created to help my blogging.

I have exported these snippets in to the file Snippets_exported.tar.gz
You can import it in “Manage Snippets” plugin. But I failed to import it, when i tried. Instead you can extract the zip file in to ~/.config/gedit/snippets folder. This will work.

The details of the snippets are given below.

Bold
Tab trigger: None
Shortcut key: Ctrl+B
Snippet code:
<strong>${1:$GEDIT_SELECTED_TEXT}</strong>$0

Example:
- HTML Code
  <strong>Selected Text</strong>
- Output
  Selected Text

Italics
Tab trigger: em
Shortcut key: Ctrl+E
Snippet code:
<em>${1:$GEDIT_SELECTED_TEXT}</em>$0

Example:
- HTML Code
  <em>Selected Text</em>
- Output
  Selected Text

color
Tab trigger: color
Shortcut key: Shift+Alt+C
Snippet code:
<span style="color:${1:#A52A2A}">${2:$GEDIT_SELECTED_TEXT}</span>$0

Example:
- HTML Code
  <span style="color:#A52A2A">Selected Text</span>
- Output
  Selected Text

Block Section
Tab trigger: block
Shortcut key: Shift+Alt+B
Snippet code:
<div style="background-color:#f0f0f3;padding:.8em;">${1:$GEDIT_SELECTED_TEXT}</div>   $0

Example:
- HTML Code
  <div style="background-color:#f0f0f3;padding:.8em;">Here is a new Block Section</div>  
- Output
  Here is a new Block Section

Wrap Selection as Link
Tab trigger: ref
Shortcut key: Shift+Alt+L
Snippet code:
<a style="color:#3366ff;" href="${1:$GEDIT_SELECTED_TEXT}" title="${2:$GEDIT_SELECTED_TEXT}" target="_blank">${3:$GEDIT_SELECTED_TEXT}</a>$0

Example:
- HTML Code
  <a style="color:#3366ff;" href="https://vishnupalakkal.wordpress.com/" title="https://vishnupalakkal.wordpress.com/" target="_blank">https://vishnupalakkal.wordpress.com/</a>
- Output
  https://vishnupalakkal.wordpress.com/

Br
Tab trigger: br
Shortcut key: Ctrl+R
Snippet code:
<br> $0

Example:
- HTML Code
  Brek after this <br> Text in Next line
- Output
  Brek after this
  Text in Next line

code box1
Tab trigger: code
Shortcut key: None
Snippet code:
<span style="display:inline-block;color:#fdfdfd;padding:.2em;background-color:#8f8f8f;border:#bbcddc 2px solid;"><strong><code>${1:Paste your code Here!}</code></strong></span>

Example:
- HTML Code
  <span style="display:inline-block;color:#fdfdfd;padding:.2em;background-color:#8f8f8f;border:#bbcddc 2px solid;"><strong><code>Paste your code Here!</code></strong></span>
- Output
  Paste your code Here!

code box2
Tab trigger: codeX
Shortcut key: None
Snippet code:
<div> ${1:Text just above code Here!}<div style="padding:.4em;background-color:#f8f9fa;border:#bbcddc 2px solid;"> [code language="${2:html}" gutter="${3:true}"] ${4:Paste your code Here for Syntax Highlighted Code!} [/code] </div><br> </div> $0

Example:
- HTML Code
  <div> Text just above code Here!<div style="padding:.4em;background-color:#f8f9fa;border:#bbcddc 2px solid;"> [code language="html" gutter="false"] Paste your code Here for Syntax Highlighted Code! [/code] </div><br> </div>
- Output
  Text just above code Here!
  Paste your code Here for Syntax Highlighted Code!

About default shell in ubuntu – “sh”, “dash”, “bash” and startup files

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The default system shell (not login shell), sh is a symbolic link. By default, in Ubuntu (from Ubuntu 6.10 onwards) it is pointing to /bin/dash. So if you use #!/bin/sh or run a command using sh command , it will not execute as ‘bash’ script, instead it will execute as ‘dash’ script.

dash is a lightweight replacement for bash, but it will not support all the bash commands. For more info, see https://wiki.ubuntu.com/DashAsBinSh
For bash vs dash, see following presentations at
http://princessleia.com/plug/2008-JP_bash_vs_dash.pdf
http://tinyurl.com/3mv8gy

Check which “sh” shell

Use below code to check which shell sh is pointing to
ls -l /bin/sh

or, get the full path of link using
readlink -f /bin/sh
or
python -c 'import os.path; print(os.path.realpath("/bin/sh"))'

Change “sh” shell

Create a symlink for sh to bash using the following command
sudo ln -sf bash /bin/sh

You can revert back to the system default by
sudo ln -sf dash /bin/sh

Note: Default login shell is still bash. Also when you open a terminal, the default shell for the terminal is bash. you can check this using echo $SHELL or ps

Startup files for bash

Startup files are invoked depends upon the shell category, such as login/non-login, interactive/non-interactive.

see some of the examples under these shell category

Shell Invocation	Login	Interactive
ssh login	yes	yes
Opening terminal window(default)	no	yes
with bash -l or -login flag	yes	*
Shell script (#!/bin/bash)	no	no

A login shell reads startup files in the following order:

/etc/profile
~/.bash_profile
~/.bash_login
~/.profile

Note: By default, the file ~/.profile contain the following lines

# if running bash

if [ -n "$BASH_VERSION" ]; then

    # include .bashrc if it exists

    if [ -f "$HOME/.bashrc" ]; then

	. "$HOME/.bashrc"

    fi

fi

So ~/.bashrc file also sourced for login shell, if it exists

When an interactive shell that is not a login shell is started, bash reads and executes commands from /etc/bash.bashrc and ~/.bashrc

When bash is started non-interactively, to run a shell script, for example, it looks for the variable BASH_ENV in the environment, expands its value if it appears there, and uses the expanded value as the name of a file to read and execute.

For more info, see man page of bash

Note: If you want to set some environmental varibles like PATH globally, you can do it in ~/.bashrc. For more info on “how to set and where to set”, see EnvironmentVariables

For more detailed information about the shell, like login/non-login, interactive/non-interactive shells and their start up files, see
http://docs.slackware.com/howtos:cli_manual:shells

Run Matlab script from a shell script – using command line

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Suppose you have a matlab script file matlab_func.m inside the directory
matlab_script_directory. Also matlab_func(string_argument,numerical_argument) takes the string_argument in the form ‘some string’ and numerical_argument (like 28, 49.0 etc).

In your bash script, you want to execute matlab_func() with arguments passed from bash script and return to the bash shell for executing further commands following it. Use the following in your bash script

# Create Matlab script file 
temp_mat_script="matlab_script_directory/run_mat_script.m"
string_argument="some string"
numerical_argument="28"
echo "matlab_func('$string_argument',$numerical_argument);" > $temp_mat_script # create new file and write 
echo "exit" >> $temp_mat_script # append to file

# Execute Matlab script file
curr_dir=$PWD
cd matlab_script_directory
matlab -nojvm -nodisplay -nosplash -r run_mat_script 
cd $curr_dir

# Delete temporary file
rm $temp_mat_script

Note: Instead of changing directory to matlab_script_directory, you can use
echo "addpath matlab_script_directory" > matlab_script_directory/,
if run_mat_script.m is created in your current directory.

Note: If the “matlab” command ( application script file) location is not
included in the PATH variable, then you need to specify as Path_To_Matlab_Command/matlab.Otherwise add it to PATH variable as

export PATH=$PATH:Path_To_Matlab_Command

You can add the above code to ~/.bashrc file, to make it permanent.

Get list of files within directories and subdirectories recursively and Format the display of file list

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If you want display a list of files under a directory recursively, see the following example.
I have the following directory structure "some_directory/sudirectory*/*.filetype"
I wanted to display file list in the following format

-------------------------- sudirectory1/1.filetype sudirectory1/2.filetype ... sudirectory2/1.filetype ... ... --------------------------

You can use one of the following methods to do the above task.

Using “ls” command
```
          cd some_directory
          ls -1 */*.filetype
          
```
Here -1 option is provided to list one file per line.

Note: Don’t use the above wild card search pattern in double quotes,
i.e, ls -1 "*/*.filetype" will not work.

Using “find” and “awk” command

Note: For familiarizing with “awk”, see some “awk” example at awk.examples
- Method-1: using awk with field separator
```
          find some_directory -name "*.mfc" -type f | awk -F"some_directory/" '{ print $2 }'
          
```
  Here we used awk command, for not to display some_directory/ in front of the file names.
- Method-2: From current directory, using awk with field separator for “./”
```
          cd some_directory
          find . -name "*.mfc" -type f | awk -F"[.]/" '{ print $2 }'
          
```
  Here we used awk command, for not to display “./” in front of the file names.
  
  Note: If you use "./" for matching, then as per regular expression it will match “any_character/”, ie “a/”, “b/” etc. will be matched. To use dot “.” as such for matching, use “[.]”
- Method-3: From current directory, using awk with substring substitution
```
          cd some_directory
          find . -name "*.mfc" -type f | awk '{ gsub("[.]/",""); print }'
          
```
  Here we used awk command as a way for string substitution, so as not to display “./” in front of the file names.
  
  Note: If you use "./" for matching, then as per regular expression it will match “any_character/”, ie “a/”, “b/” etc. will be matched. To use dot “.” as such for matching, use “[.]”

Some differences between usages of “csh” and “bash” scripting

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Useful website links
- Differing Shell Features
- Translate between bash and tcsh commands
Shell variables assignment
bash:
```
x=3
```
csh:
```
set x = 3
```
Note: spaces are important in bash where as it is not important in csh

Environmental variables assignment
bash:
```
export z=5
```
csh:
```
setenv z 5
```

Integer Expression
bash:
```
j=$((i-1))
```
Or
```
let j=i-1
```
csh:
```
@ j = $i - 1
```

for loop

bash:

               for i in 1 2 3
               do
               echo Iteration Number $i
               #let j=i-1
               j=$((i-1))
               done

csh:

              foreach i (1 2 3 )
                @ j = $i - 1
              end

Valid and Invalid Variable Substitution
${var} will work in both csh and bash.
But {$var} work in csh but not in bash.
See eg:
```
csh -c "echo {$HOME}1"
```
will works in csh but in bash we need the following
```
bash -c "echo ${HOME}1"
```

Array: declaration, iterate, first item, count

bash:

             snr=(clean1 N1_SNR20 N1_SNR15 N1_SNR10 N1_SNR5 N1_SNR0) # array declaration
             snr_array_length=${#snr[@]} # get array size
             snr_first_item=${snr[0]} # get first item, starts at index 0
             first_item_length=${#snr[0]} # get length of first item

csh:

             set snr = (clean1 N1_SNR20 N1_SNR15 N1_SNR10 N1_SNR5 N1_SNR0) # array declaration
             set snr_array_length = $#snr # get array size
             set snr_first_item = $snr[1] # get first item, starts at index 1

While loop with array

bash:

             snr=(clean1 N1_SNR20 N1_SNR15 N1_SNR10 N1_SNR5 N1_SNR0)
             count=0
             snr_array_length=${#snr[@]}
             while [ $count -lt $snr_array_length ]
             do
                printf "\n Noise condition: %s\n" ${snr[$count]}
                let count+=1
             done

csh:

             set snr    = (clean1 N1_SNR20 N1_SNR15 N1_SNR10 N1_SNR5 N1_SNR0)
             set count  = 1
             while ($count <= $#snr)
                printf "\n Noise   condition: %s\n" $snr[$count]
                @ count++
             end

Behaviour of “Exit” command with sourcing
In bash:
“exit” command, will exit the shell where the “source” command was executed, as it is that shell which reads each command in turn and executes it. In contrast in a standalone script (if executed, not sourced) the “exit” command will exit only out of the shell/interpreter which was started to execute the commands in the script. Therefore the executed script file will just stop and return to the shell which called it.
The danger is therefore if a standalone script is sourced instead of being executed. If in that script file there is an “exit” command then the shell which called the script will be exited and not just the script.

For example, content of ‘sample_bash.sh’ is
```
             #!/bin/bash
             echo "bash-Shell script started"
             exit
             echo "bash-Shell script not exited from sample_bash.sh"
             
```
then output of
```
             bash -c 'bash sample_bash.sh
              echo "not exited completely"'
             
```
is

bash-Shell script started
not exited completely

But output of
```
             bash -c 'source sample_bash.sh
              echo "not exited completely"'
             
```
is

bash-Shell script started
In csh:
“exit” command in sourced script, will not behave as expected. It just stop and return to the shell which called it.

For Example, output of
```
             csh -c 'source sample_csh.csh
              echo "not exited completely"'
             
```
is

C-Shell script started
not exited completely

Useful website links containing linux and shell script tips

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Shell script tutorial links

String Manipulation
- Links:
  http://tldp.org/LDP/abs/html/string-manipulation.html
- Substring Removal
  ${string#substring} Deletes shortest match of $substring from front of $string. ${string##substring} Deletes longest match of $substring from front of $string. ${string%substring} Deletes shortest match of $substring from back of $string. ${string%%substring} Deletes longest match of $substring from back of $string.
- Substring Replacement
  ${string/substring/replacement} Replace first match of $substring with $replacement. ${string//substring/replacement} Replace all matches of $substring with $replacement. ${string/#substring/replacement} If $substring matches front end of $string, substitute $replacement for $substring. ${string/%substring/replacement} If $substring matches back end of $string, substitute $replacement for $substring.

Website hosting on local host

Useful website links containing wordpress tricks

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For scroll boxes and useful text formatting tips

see http://wpbtips.wordpress.com/
Links
Note
- Code for vertical scroll box
```
<div style="height:150px;white-space:pre-wrap;overflow:auto;padding:8px;">
```
- Code for horizontal scroll box
```
<div style="white-space:pre;overflow:auto;padding:8px;">
```

Set as block of text by light gray background

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To set block of text in separate background.

Use the below code

<div style="background-color:#f0f0f3;padding:0.8em;">
Your block of Text here
Your block of Text here
Your block of Text here
Your block of Text here
</div>

It will perceive as a separate note or block like this

Your block of Text here
Your block of Text here
Your block of Text here
Your block of Text here

Display lines containing a pattern from a file using “grep”

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To display lines which contains “pattern” from a file. Use grep command as

grep pattern file_name

Use -v option to display lines that does not contain pattern

Eg:-
Here I want to include lines containing “testa/N1_SNR” pattern, but exclude lines containing “testa/N1_SNR-” pattern and concatenate with content of other file.

I use below code

{ grep "testa/N1_SNR" all_hcopy.scp | grep -v "SNR-" ; cat CleanTR08_hcopy.scp ; } > only_testa_N1.scp

Use { cmd1; cmd2; } to execute all commands in the current shell
see http://mywiki.wooledge.org/BashSheet#Command_Lists

Grep recursively, but only certain file extensions

Use the below code
grep -r --include="file_pattern" "Pattern_To_search" Directory_Path
For example:
To search all the files with extension “.m”, and find lines in these files containing the word gmm
grep --include="*.m" -nRHIi "gmm" .

Note: Here the options specified are
-r or -R for recursive search
-n Prefix each line of output with the line number within its input file.
-H Print the filename for each match
-I Process a binary file as if it did not contain matching data; this is equivalent to the –binary-files=without-match option
-i for case insensitive search

See more usages of grep command at using-grep-regular-expressions-to-search-for-text-patterns-in-linux

Change color of the text

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Use the code

<span style="color:#3366ff;"> blue text </span>

to get
blue text
I use this color for website links.

see styling-individual-posts-and-pages for more text formatting tips

About vishnupalakkal

Bold

Italics

color

Block Section

Wrap Selection as Link

Br

code box1

code box2

Check which “sh” shell

Change “sh” shell

Startup files for bash

Using “ls” command

Using “find” and “awk” command

Method-1: using awk with field separator

Method-2: From current directory, using awk with field separator for “./”

Method-3: From current directory, using awk with substring substitution

For scroll boxes and useful text formatting tips

Grep recursively, but only certain file extensions