How to remove space from string?

Question

In ubuntu bash script how to remove space from one variable

string will be

   3918912k

Want to remove all blank space.

http://stackoverflow.com/questions/369758/how-to-trim-whitespace-from-bash-variable — cnicutar, Dec 01 '12 at 12:13
trimming everything, at start, at the end and all in the midle: echo ' aaa bb c'|xargs -L1 echo it is all. of course you can change -L1 into -n1 , then all strings will be converted into separate lines. — Znik, Jun 30 '23 at 06:10

score 170 · Answer 1 · edited Jun 30 '16 at 03:12

170

The tools sed or tr will do this for you by swapping the whitespace for nothing

sed 's/ //g'

tr -d ' '

Example:

$ echo "   3918912k " | sed 's/ //g'
3918912k

edited Jun 30 '16 at 03:12

ti7

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answered Dec 01 '12 at 17:51

squiguy

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Works perfectly. This should be the accepted answer. – phpguru Jul 15 '15 at 15:43
Indeed, the currently accepted answer is not POSIX. For portable scripts, this answer is better. – MoonSweep Dec 18 '16 at 16:26
How can I use it to save the result in a variable? Does it only work in `echo`? I'm having some trouble. Is it supposed to work like: `RESULT="$STR" | set "s/ //g"` ? – cbdeveloper Feb 16 '21 at 18:18
@cbdeveloper you could do this: `RESULT=$(sed "s/ //g" <<< $STR)` – Mattias Oct 28 '21 at 22:27
Does not work for strip newlines but only for blank spaces on a one line – e-info128 Jun 16 '23 at 01:39

Gilles Quénot · Accepted Answer · 2020-11-22T00:22:28.530

105

Try doing this in a shell:

var="  3918912k"
echo ${var//[[:blank:]]/}

That uses parameter expansion (it's a non posix feature)

[[:blank:]] is a POSIX regex class (remove spaces, tabs...), see http://www.regular-expressions.info/posixbrackets.html

edited Nov 22 '20 at 00:22

answered Dec 01 '12 at 12:14

Gilles Quénot

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Substitution inside parameter expansion isn't POSIX. It will work in Bash (and maybe other shells I don't know), but not in Dash for example. – MoonSweep Dec 18 '16 at 16:25
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This one works also: str="${str// /}" – Tsounabe Sep 23 '19 at 22:12

Tim Pote · Answer 3 · 2012-12-01T16:58:35.890

7

Since you're using bash, the fastest way would be:

shopt -s extglob # Allow extended globbing
var=" lakdjsf   lkadsjf "
echo "${var//+([[:space:]])/}"

It's fastest because it uses built-in functions instead of firing up extra processes.

However, if you want to do it in a POSIX-compliant way, use sed:

var=" lakdjsf   lkadsjf "
echo "$var" | sed 's/[[:space:]]//g'

edited Dec 01 '12 at 16:58

answered Dec 01 '12 at 16:42

Tim Pote

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In a non-interactive shell (i.e. a script), you need to `shopt -s extglob` for the first one. – glenn jackman Dec 01 '12 at 16:56
1

@glennjackman Good catch. See my updates. – Tim Pote Dec 01 '12 at 16:58

score 5 · Answer 4 · answered Dec 01 '12 at 13:45

5

You can also use echo to remove blank spaces, either at the beginning or at the end of the string, but also repeating spaces inside the string.

$ myVar="    kokor    iiij     ook      "
$ echo "$myVar"
    kokor    iiij     ook      
$ myVar=`echo $myVar`
$
$ # myVar is not set to "kokor iiij ook"
$ echo "$myVar"
kokor iiij ook

answered Dec 01 '12 at 13:45

Mickaël Le Baillif

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This is not reliable : if `myVar` contains special characters like `*`, the shell will expand it with the files of the current directory. – Gilles Quénot Dec 01 '12 at 15:24
As #bash on freenode always says... use more quotes. `echo "$myvar"` prevents expansion of globs, etc. – bobpaul Mar 04 '14 at 20:01
@bobpaul, it prevents expansion of globs, etc, but also includes the leading and trailing whitespaces Mickaël intended to get rid of :( – Gui Prá Sep 26 '15 at 20:02

gniourf_gniourf · Answer 5 · 2012-12-01T17:12:02.560

A funny way to remove all spaces from a variable is to use printf:

$ myvar='a cool variable    with   lots of   spaces in it'
$ printf -v myvar '%s' $myvar
$ echo "$myvar"
acoolvariablewithlotsofspacesinit

It turns out it's slightly more efficient than myvar="${myvar// /}", but not safe regarding globs (*) that can appear in the string. So don't use it in production code.

If you really really want to use this method and are really worried about the globbing thing (and you really should), you can use set -f (which disables globbing altogether):

$ ls
file1  file2
$ myvar='  a cool variable with spaces  and  oh! no! there is  a  glob  *  in it'
$ echo "$myvar"
  a cool variable with spaces  and  oh! no! there is  a  glob  *  in it
$ printf '%s' $myvar ; echo
acoolvariablewithspacesandoh!no!thereisaglobfile1file2init
$ # See the trouble? Let's fix it with set -f:
$ set -f
$ printf '%s' $myvar ; echo
acoolvariablewithspacesandoh!no!thereisaglob*init
$ # Since we like globbing, we unset the f option:
$ set +f

I posted this answer just because it's funny, not to use it in practice.

However in this case, the quotes are explicitly missing in order to remove the leading whitespace. So glob chars are in play. — glenn jackman, Dec 01 '12 at 16:57
Condensed to a safe one line: `myvar="$( set -f; printf "%s" $myvar )"; echo "[$myvar]"` — , Jul 28 '15 at 03:10

How to remove space from string?

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