Replace tabs with spaces linux cmd

Convert Tabs to Spaces in Linux Terminal With Expand Command

The debate over the use of tabs and spaces in the programming is a never ending one.

While you may prefer using tabs all the time, chances are that your coding guideline suggest using spaces.

But if you have already used tabs everywhere into your program and you need to convert those tabs into spaces so that the reviewer allows your code, you are at the right place.

In this tutorial, I’ll show you how to convert the tabs into spaces in a text file in Linux command line.

Using expand command to convert tabs into spaces in Linux command line

I am using this sample text file which is a simple C++ program for checking odd and even number. This is the content of the file:

You can download this file from here if you want to practice the command while following this tutorial.

Check if your text file has tabs

There are several ways of doing it. The simplest method I find is by using the cat command.

You can use the cat command with option -T and will display all the tabs as ^I on the screen (stdout).

You can see the location of the tabs in the file.

File with tabs

Convert tabs into spaces with expand command

If you use expand command on a file, it will convert all the tabs into a block of 8 spaces and will display the output on the screen.

But that’s not very convenient, is it? You will hardly see the changes here. A better idea would be to save the output to another file.

Now if you see the file using the cat command, you won’t find any tabs anymore.

All tabs converted into 8 spaces (default)

Reduce the number of spaces

As I mentioned in the previous section, by default, a tab is equal to 8 spaces. That would look super weird if your code has such huge indentation.

The good thing is that you can change the default space size with the -t option.

For example, if you have to change each tab into 2 spaces, you can use the expand command like this:

All tabs converted into 2 spaces

Convert only leading tabs into spaces

Often in the programs, you would only want to convert the leading tabs i.e. the tabs at the beginning of the line. You don’t want to touch the tabs in between the lines that are actually part of the code.

Expand provides this option as well. If you want to only convert the leading tabs into spaces, use the –i option.

If we continue the previous example, here is what the command would look like:

Only leading tabs converted into spaces

Convert tabs into spaces and save it to the original file

In all the above examples, you have saved the converted file into a new file. But if your aim is to clean your code by convert the tabs into spaces of the existing program files, you would want the output to be saved in the original file itself.

To do that, you can use the sponge command. Sponge ‘soaks up’ the entire standard input before writing it to output. This is extremely useful when you are trying to change and save the same file.

Now, the sponge command may not be available on your system. You’ll have to install the moreutils package. It should be available

On Ubuntu/Debian based distributions, you can use this command to install moreutils:

Once installed, you can use it in the following function:

Convert tabs into spaces in all the matching files in a directory

Till now whatever you learned was applicable to a single file. But if you have a project that has several program files and you want to convert the tabs into spaces in all of them, you’ll have to be a bit more smart here.

What we have learned so far can be combined with the magnificent find and exec commands.

The above command finds all the files ending with extension cpp, pass these files to the expand command and the expand command writes the output to the original files with the help of sponge command.

You might think using sed command would have been easier at this point but that’s entirely your choice.

Источник

Bash Shell: Convert Tabs To Spaces In a File

H ow do convert tabs to spaces in a file using a bash shell?

You can use various tools. The expand command converts all tabs to spaces. It preserves backspace characters in the output; they decrement the column count for
tab calculations.

The -t option can be used to set comma separated list of explicit tab positions. You can use the unexpand command convert spaces to tabs. See man page for more info:
man expand
man unexpand

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Comments on this entry are closed.

My imput.file looks like:
$ cat input.file
tux Linux
tux Linux
tux Linux
tux Linux
$
But executing expand on the file showing the same format(in STDOUT) as input.file…
$ expand input.file
tux Linux
tux Linux
tux Linux
tux Linux
$
Though I am getting the expected result with “tr” command.
I am using CentOS 5.3(x86_64); Any comment ?

That’s because expand expects 2 tabs (=8 charachter spaces) as default tab.
So it doesn’t a tab in your file.
The command expand -t1 wil work with your file, as t1 means 4 spaces

You can also use perl:
perl -pi -e ‘s/\t/ /’ file.name

s are truncated in my posts itself 🙂

expand fails miserably on multibyte characters (i.e. on non-ASCII characters in UTF-8 encoding)
still as of coreutils 8.21 (2013)

Its working for me
Tab space conver into space
expand -t 2 file | mailx -s “xxxx” email@add.com

expand doesn’t seem to do the right thing.
Converting tabs to spaces in a piece of content is more than merely translating each tab character to a sequence of space characters. It needs to preserve the alignment of the text. So in this example text (no quotes):
“Foo\tBar\tBazinga!”
and with a tab spacing of 3 chars, the result should be (each period corresponds to a white space):
“Foo…Bar..Bazinga!”
This way the de-tabbed content would overlay the original content exactly (assuming the same tab setting).

Typo in my example, and not a great example. Let’s try this one instead:
“Foo\tBars\tBazinga!”
and with a tab spacing of 4 chars, the result should be (each period corresponds to a white space):
“Foo.Bars….Bazinga!”

Note how each tab char was not replaced with 4 spaces.

Источник

Converting tabs to spaces

created 2001 · complexity basic · author Yegappan · version 5.7

Contents

Settings [ ]

To insert space characters whenever the tab key is pressed, set the ‘expandtab’ option:

With this option set, if you want to enter a real tab character use Ctrl-V key sequence.

To control the number of space characters that will be inserted when the tab key is pressed, set the ‘tabstop’ option. For example, to insert 4 spaces for a tab, use:

After the ‘expandtab’ option is set, all the new tab characters entered will be changed to spaces. This will not affect the existing tab characters. To change all the existing tab characters to match the current tab settings, use:

To change the number of space characters inserted for indentation, use the ‘shiftwidth’ option:

For example, to get the following coding style,

• No tabs in the source file.
• All tab characters are 4 space characters.

use the following set of options:

or as a oneliner:

Add the above settings to your vimrc.

Adjusting indent [ ]

Since tabs effectively group spaces together, you may be tempted to work with tabs rather than spaces and change individual lines selectively. To easily change a tab-based indent to use spaces instead when ‘noexpandtab’ is set, you can temporarily set ‘expandtab’ and use :retab with a range. For example, to convert only the current line to use spaces, use :.retab .

However, with some configuration, Vim makes working with spaces for indentation as easy as working with tabs. You can always use the operators to quickly indent/de-indent lines or visual selections. And you can set the ‘softtabstop’ option to cause and to insert and delete the correct number of spaces.

See also [ ]

• Super retab to change only indents (whitespace at left margin)
• Highlight unwanted spaces to display unwanted whitespace

References [ ]

Comments [ ]

To turn off expandtab for editing makefiles, put the following in your vimrc:

To use this mode only for Python add the following to your vimrc:

This is what I use for Python:

I also add the following line:

This makes the backspace key treat the four spaces like a tab (so one backspace goes back a full 4 spaces).

It is possible to get vim to insert at the «true» start of the line with soft tabs, if you have:

I change these so frequently that I have keystrokes bound to switch between them:

I use this to insert spaces at the beginning of a line and real tab characters elsewhere:

If you’re trying to figure out how it works and are confused by the thing: = asks for an expression, and the expression is entered as if it was typed, then the return value of the expression is inserted as if it too was typed — so, we want to insert , but if we just entered that into the expression, it would be converted to before the expression is executed — so, we have to enter into the expression, which will be converted to before the expression is executed, which will then become in the actual file.

I also remapped Shift-Tab so I could easily insert real tabs at the beginning of the line when necessary:

Источник

Sed Tab Space

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