A tab is not made out of spaces. It is a tab, whether in Java, Python, Rust, or generic text file editing. It is represented by a single Unicode character, U+0009.
It does not generally mean “insert this many spaces here” either. It means “put the cursor at the next closest tab stop in the line”. What that means exactly depends on the context. On an old typewriter I had, a tab key would advance the roller to the next column that was a multiple of 10
That is pretty much the same function as the tab character does.
Just for reference, modern text editors have their tab stops set to either every 4 or every 8 characters. That doesn’t mean that 1 tab = 4/8 spaces, that means that putting in a tab will align the cursor with the next multiple of 4/8 columns
In mainstream IDEs you can set the tab key to insert a desired number of spaces instead of a tab character.
The concept of tab independent of space is rarely used these days. In any case, what the character represents is decoupled from what the key does is decoupled from what the screen shows.
In many IDEs, the tab character inserts the required number of spaces to advance to the next tab line. This is often a default.
I imagine it’s a compromise between tab loving extremists and space advocates. The ideal whitespace character is a subject of intense debate among programmers.
Please note that this is a basic cheat sheet and git has many more functionalities and options, it is worth reading the git documentation to learn more.
Clone a project: git clone git_repo_url project_name
Switch to a branch locally: git checkout branch_name
Modify a file, then save and push it to remote repo in current branch git add path_to_file_modifeid/file_name git commit -m “Description of modification” git push
Get a new version of a file after modifying local version git checkout path_to_file_modified/file_modified
Get latest version of current branch git fetch git pull if you have local changes, you will be prompted to commit or stash them before pulling.
Create a new branch based on current branch and switch to it git checkout –b branch_name
Switch to master branch git checkout master
Merge branch_name to master git merge branch_name
Delete local branch git branch -d branch_name
Undo a merge or pull git reset –hard
Undo a commit locally and on the remote branch git reset –hard commit_id git push –force
Get remote url of a local branch git remote show origin
How to declare and write a script with hash tables on windows and linux
A hash table, also known as a hash map, is a data structure that is used to store key-value pairs. It is an efficient way to store data that can be quickly retrieved using a unique key.
Here is an example of how to declare and write a script with a hash table in Python:
# Declare an empty hash table hash_table = {}
# Add some key-value pairs to the hash table hash_table[‘key1’] = ‘value1’ hash_table[‘key2’] = ‘value2’ hash_table[‘key3’] = ‘value3’
# Access a value using its key print(hash_table[‘key2’]) # Output: “value2”
# Modify a value using its key hash_table[‘key2’] = ‘new value’ print(hash_table[‘key2’]) # Output: “new value”
# Delete a key-value pair using the `del` statement del hash_table[‘key1’]
# Check if a key is in the hash table using the `in` operator print(‘key1’ in hash_table) # Output: False
# Output: False
In this example, we declare an empty hash table using the {} syntax. We then add some key-value pairs to the hash table using the [] syntax. We access a value using its key, modify a value using its key, delete a key-value pair using the del statement, and check if a key is in the hash table using the in operator.
I hope this helps! Let me know if you have any questions.
Add new key-value in hashtable: $states.Add(“Manitoba”,”Winnipeg”)
Remove key-value in hashtable: $states.Remove(“Manitoba”,”Winnipeg”) Change value in hashtable: $states.Set_Item(“Ontario”,”Ottawa”) Retrieve value in hashtable: $states.Get_Item(“Alberta”) Find key in hashtable: $states.ContainsKey(“Alberta”) Find Value in hashtable: $states.ContainsValue(“Calgary”) Count items in hashtable: $states.Count Sort items by Name in hashtable: $states.GetEnumerator() | Sort-Object Name -descending Sort items by Value in hashtable: $states.GetEnumerator() | Sort-Object Value -descending
Hash tables with perl on linux or windows
Declaration: my %hash = (); #Initialize a hash my $hash_ref = {}; # Initialize a hash reference. ref will return HASH Clear (or empty) a hash for (keys %hash) { delete $hash{$_}; } Clear (or empty) a hash reference for (keys %$href) { delete $href->{$_}; } Add a key/value pair to a hash $hash{ ‘key’ } = ‘value’; # hash $hash{ $key } = $value; # hash, using variables Using Hash Reference $href->{ ‘key’ } = ‘value’; # hash ref $href->{ $key } = $value; # hash ref, using variables Add several key/value pairs to a hash %hash = ( ‘key1’, ‘value1’, ‘key2’, ‘value2’, ‘key3’, ‘value3’ ); %hash = ( key1 => ‘value1’, key2 => ‘value2’, key3 => ‘value3’, );
Copy a hash my %hash_copy = %hash; # copy a hash my $href_copy = $href; # copy a hash ref Delete a single key/value pair delete $hash{$key}; delete $hash_ref->{$key};
On both Windows and Linux, you can use the grep command in combination with the | (pipe) operator to filter the output of another command. The | operator takes the output of the command on the left and passes it as input to the command on the right.
Here is an example of how to use the grep command with the | operator on both Windows and Linux:
On Linux:
# List all the files in the current directory and filter the output to show only the files that contain the word "example" ls | grep example
On Windows:
# List all the files in the current directory and filter the output to show only the files that contain the word "example" dir | findstr example
In this example, the ls (Linux) or dir (Windows) command lists all the files in the current directory, and the grep (Linux) or findstr (Windows) command filters the output to show only the lines that contain the word “example”.
You can use the grep command with the | operator in combination with other command-line utilities to perform various tasks. For example, you can use the grep command to filter the output of the ps command to show only the processes that contain a particular string in their command line arguments.
Using the rev command: The rev command is a utility that reverses the lines of a file or the characters in a string. To reverse a string, you can use the echo command to pass the string to rev:
echo"string" | rev
Using the sed command: The sed command is a powerful utility that can perform various text transformations. To reverse a string, you can use the sed command with the -r option and the 's/.*(.)/\1/g' expression:
echo"string" | sed -r 's/.*(.)/\1/g'
Using the awk command: The awk command is a programming language that is used for text processing. To reverse a string, you can use the awk command with the {print} action:
echo"string" | awk '{print $1}'
On Windows:
Using the powershell command: The powershell command is a shell that provides a command-line interface for Windows. To reverse a string, you can use the powershell command with the -C option and the '[System.Text.Encoding]::Unicode.GetString([System.Text.Encoding]::Unicode.GetBytes("string"))' expression:
Using the cmd command: The cmd command is the command-line interpreter for Windows. To reverse a string, you can use the cmd command with the for loop:
cmd /c "for /L %i in (1,1,%len%) do @echo !string:~%len%-%i,1!"
These are some ways to reverse a string on Linux and Windows. There are other ways to achieve this, using different utilities or programming languages.
Via shell script on Linux
sh-3.2# vi reverse.sh #### Start Script ##### #!/bin/bash input_string=”$1″ reverse_string=””
input_string_length=${#input_string} for (( i=$input_string_length-1; i>=0; i– )) do reverse_string=”$reverse_string${input_string:$i:1}” done
::—————- :: Calc Var Length ::—————- :: %*=Str to Check :: Returns %Len% :: ————— :StrLen %* set Data=%* for /L %%a in (0,1,80) do ( set Char=!Data:~%%a,1! if not “!Char!”==”” ( set /a Len=%%a+1 ) else (exit /b) ) exit /b
::————— :: Reverse String ::————— :: %* Str to Reverse :: Returns %Reverse% ::—————— :ReverseStr %* set Data=%* call :StrLen %Data% for /L %%a in (!Len!,-1,0) do ( set Char=!Data:~%%a,1! set Reverse=!Reverse!!Char! ) exit /b
Let’s find how to prompt and read input variables from keyboard while executing a script using shell, perl, python, batch and powershell (windows and Linux)
On Linux via shell
read -p “Enter your name: ” name echo “Hi, $name. Let’s be friend!”
On Windows via powershell
$name=read-host “Enter your name:” write-host “Hi $name, Let’s be friend!”
On Windows via batch
Set /p Name=”Enter your name:” echo “Hi %name%, Let’s be friend!”
On Windows or Linux via perl
print “Enter your name “; my $name = ; chomp $name; # Get rid of newline character at the end print “Hello $name, let’s be friend”;
On Windows or Linux via python
name=input(“Enter your name: “) print (“Hello ” + name + ” let’s be friend”)
How to search all files containing a specific string on Linux and Windows?
On Linux
grep -rnw ‘directory’ -e “pattern” grep –include=\*.{txt,log} -rnw ‘directory’ -e “pattern” This will only search for files with .txt or .log extension. grep –exclude=*.txt -rnw ‘directory’ -e “pattern” This will exclude files with .txt extensions.
On Windows
CD Location FINDSTR /L /S /I /N /C:”pattern” *.log
How to browse the internet via command line on Linux and Windows?
On Linux
lynx http://google.ca If you don’t have lynx on your linux installation, you will have to install it. On Linux Red hat, install it like this: yum list lynx (to check the availability of the package) yum -y install lynx (to install the package) you can also use: curl -0 http://yoursite/index.html to get the source code of a specific file.
On Windows
start /max http://google.ca Will open the url using your default browser.
Today I Learned (TIL) You learn something new every day; what did you learn today? Submit interesting and specific facts about something that you just found out here.
submitted by /u/Hopeful-Candle-4884 [link] [comments]
Reddit Science This community is a place to share and discuss new scientific research. Read about the latest advances in astronomy, biology, medicine, physics, social science, and more. Find and submit new publications and popular science coverage of current research.