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SED - Remove white-space

Remove all whitespace (including tabs) from beginning of string

echo "     This is a test" | sed -e 's/^[ \t]*//'

result:

This is a test

Where,

s/ : Substitute command ~ replacement for pattern (^[ \t]*) on each addressed line
^[ \t]* : Search pattern ( ^ – start of the line; [ \t]* match one or more blank spaces including tab)
** : Replace (delete) all matched pattern —-