Replace whitespaces with tabs in linux

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

Using sed:

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

or

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

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