Replace whitespaces with tabs in linux

How do I replace whitespaces with tabs in linux in a given text file?

Use the unexpand(1) program

---

UNEXPAND(1)                      User Commands                     UNEXPAND(1)

NAME
       unexpand - convert spaces to tabs

SYNOPSIS
       unexpand [OPTION]... [FILE]...

DESCRIPTION
       Convert  blanks in each FILE to tabs, writing to standard output.  With
       no FILE, or when FILE is -, read standard input.

       Mandatory arguments to long options are  mandatory  for  short  options
       too.

       -a, --all
              convert all blanks, instead of just initial blanks

       --first-only
              convert only leading sequences of blanks (overrides -a)

       -t, --tabs=N
              have tabs N characters apart instead of 8 (enables -a)

       -t, --tabs=LIST
              use comma separated LIST of tab positions (enables -a)

       --help display this help and exit

       --version
              output version information and exit
. . .
STANDARDS
       The expand and unexpand utilities conform to IEEE Std 1003.1-2001
       (``POSIX.1'').

I think you can try with awk

awk -v OFS="\t" '$1=$1' file1

or SED if you preffer

sed 's/[:blank:]+/,/g' thefile.txt > the_modified_copy.txt

or even tr

tr -s '\t' < thefile.txt | tr '\t' ' ' > the_modified_copy.txt

or a simplified version of the tr solution sugested by Sam Bisbee

tr ' ' \\t < someFile > someFile

Using Perl:

perl -p -i -e 's/ /\t/g' file.txt

better tr command:

tr [:blank:] \\t

This will clean up the output of say, unzip -l , for further processing with grep, cut, etc.

e.g.,

unzip -l some-jars-and-textfiles.zip | tr [:blank:] \\t | cut -f 5 | grep jar

Example command for converting each .js file under the current dir to tabs (only leading spaces are converted):

find . -name "*.js" -exec bash -c 'unexpand -t 4 --first-only "$0" > /tmp/totabbuff && mv /tmp/totabbuff "$0"' {} \;

Download and run the following script to recursively convert soft tabs to hard tabs in plain text files.

Place and execute the script from inside the folder which contains the plain text files.

#!/bin/bash

find . -type f -and -not -path './.git/*' -exec grep -Iq . {} \; -and -print | while read -r file; do {
	echo "Converting... "$file"";
	data=$(unexpand --first-only -t 4 "$file");
	rm "$file";
	echo "$data" > "$file";
}; done;

You can also use astyle. I found it quite useful and it has several options too:

Tab and Bracket Options:
   If  no  indentation  option is set, the default option of 4 spaces will be used. Equivalent to -s4 --indent=spaces=4.  If no brackets option is set, the
   brackets will not be changed.

   --indent=spaces, --indent=spaces=#, -s, -s#
          Indent using # spaces per indent. Between 1 to 20.  Not specifying # will result in a default of 4 spaces per indent.

   --indent=tab, --indent=tab=#, -t, -t#
          Indent using tab characters, assuming that each tab is # spaces long.  Between 1 and 20. Not specifying # will result in a default assumption  of
          4 spaces per tab.`

Using sed:

T=$(printf "\t")
sed "s/[[:blank:]]\+/$T/g"

or

sed "s/[[:space:]]\+/$T/g"

This will replace consecutive spaces with one space (but not tab).

tr -s '[:blank:]'

This will replace consecutive spaces with a tab.

tr -s '[:blank:]' '\t'

If you are talking about replacing all consecutive spaces on a line with a tab then tr -s '[:blank:]' '\t'.

[root@sysresccd /run/archiso/img_dev]# sfdisk -l -q -o Device,Start /dev/sda
Device         Start
/dev/sda1       2048
/dev/sda2     411648
/dev/sda3    2508800
/dev/sda4   10639360
/dev/sda5   75307008
/dev/sda6   96278528
/dev/sda7  115809778
[root@sysresccd /run/archiso/img_dev]# sfdisk -l -q -o Device,Start /dev/sda | tr -s '[:blank:]' '\t'
Device  Start
/dev/sda1       2048
/dev/sda2       411648
/dev/sda3       2508800
/dev/sda4       10639360
/dev/sda5       75307008
/dev/sda6       96278528
/dev/sda7       115809778

If you are talking about replacing all whitespace (e.g. space, tab, newline, etc.) then tr -s '[:space:]'.

[root@sysresccd /run/archiso/img_dev]# sfdisk -l -q -o Device,Start /dev/sda | tr -s '[:space:]' '\t'
Device  Start   /dev/sda1       2048    /dev/sda2       411648  /dev/sda3       2508800 /dev/sda4       10639360        /dev/sda5       75307008        /dev/sda6     96278528        /dev/sda7       115809778  

If you are talking about fixing a tab-damaged file then use expand and unexpand as mentioned in other answers.

sed 's/[[:blank:]]\+/\t/g' original.out > fixed_file.out

This will for example reduce the amount of tabs.. or spaces into one single tab.

You can also do it for situations of multiple spaces/tabs into one space:

sed 's/[[:blank:]]\+/ /g' original.out > fixed_file.out