How to remove leading whitespace from a string in Bash

Question

For example, I have a string, " some string", and I want to put "some string" in another string variable. How do I do that?

My code:

function get_title() {
    t1=$(get_type "$1")
    t2="ACM Transactions"
    t3="ELSEVIER"
    t4="IEEE Transactions"
    t5="MIT Press"
    if [ "$t1"=="$t2" ];
        then
        title=$(less "$1" | head -1)
    elif [ "$t1"=="$t5" ];
    then
        title=$(less "$1" | head -3)
    fi
    echo "$title"
}

As you can see the $title can return unwanted whitespace in front of text in center aligned texts. I want to prevent that.

Specifically, take a look at the third code block of the [top-rated answer](http://stackoverflow.com/a/3232433/2489497) ("How to remove leading whitespace only") — Caleb Brinkman, Sep 24 '15 at 04:05
Oh, thanks. I didn't check at that question because I didn't want to trim whitespace completely. @CalebBrinkman — Shawon0418, Sep 24 '15 at 04:07

peak · Accepted Answer · 2017-05-24T20:36:05.590

15

A robust and straightforward approach is to use sed e.g.

$ sed 's/^[[:space:]]*//' <<< "$var"

If you are willing to turn on extended globbing (shopt -s extglob), then the following will remove initial whitespace from $var:

 "${var##+([[:space:]])}"

Example:

var=$' \t abc \t ' echo "=${var##+([[:space:]])}="
=abc   =

edited May 24 '17 at 20:36

answered Sep 24 '15 at 04:36

peak

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2

You can also use a capture group in a regular expression to avoid starting a new process for `sed`: `[[ $var =~ [[:space:]]*(.*) ]] && var=${BASH_REMATCH[1]}` – chepner Sep 24 '15 at 12:08

How to remove leading whitespace from a string in Bash

1 Answers1