The TrimLeft(s) command removes the leading whitespace from string s and returns the resulting terminal substring. If string s has no leading whitespace, then it is returned unchanged.

The TrimRight(s) command removes the trailing whitespace from string s and returns the resulting substring. If string s has no trailing whitespace, then it is returned unchanged.

The TrimRight function is defined by $\mathrm{TrimRight}\left(s\right)=\mathrm{Reverse}\left(\mathrm{TrimLeft}\left(\mathrm{Reverse}\left(s\right)\right)\right)$.

The Trim(s) command is defined to be the composition $\mathrm{TrimRight}\circ \mathrm{TrimLeft}$.

All of the StringTools package commands treat strings as (null-terminated) sequences of $8$-bit (ASCII) characters.  Thus, there is no support for multibyte character encodings, such as unicode encodings.

$\mathrm{with}\left(\mathrm{StringTools}\right)\:$

$s≔''\backslash t\; This\; is\; a\; test.\; \backslash n''$

$s≔''This\; is\; a\; test.''$

$\mathrm{TrimLeft}\left(s\right)$

$''This\; is\; a\; test.''$

$\mathrm{TrimRight}\left(s\right)$

$''This\; is\; a\; test.''$

$\mathrm{Trim}\left(s\right)$

$''This\; is\; a\; test.''$