The PadLeft(s, width) command adds spaces to the left of the string s to produce a string of length equal to width. If width is less than or equal to the length of s, then s is returned unchanged.

The PadRight(s, width) command adds spaces to the right of the string s to produce a string of length width. If width is less than or equal to the length of s, then s is returned unchanged.

The optional padchar argument can be used to specify that a character other than the space be used to pad the string.

The Center(s, width) command adds spaces to both ends of the string s to produce a string of length width. If width - length(s) is even, then an equal number of spaces are added to the left and right ends of s. If width - length(s) is odd, then the extra space is added to the left of s.

The StringTools[TrimLeft], StringTools[TrimRight] and StringTools[Trim] commands are approximate inverses of PadLeft, PadRight and Center, respectively.

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.

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

$\mathrm{PadLeft}\left(''foo''\,2\right)$

$''foo''$

$\mathrm{PadLeft}\left(''foo''\,3\right)$

$''foo''$

$\mathrm{PadLeft}\left(''foo''\,4\right)$

$''foo''$

$\mathrm{PadLeft}\left(''foo''\,5\right)$

$''foo''$

$\mathrm{PadLeft}\left(''foo''\,6\right)$

$''foo''$

$\mathrm{PadRight}\left(''foo''\,5\right)$

$''foo''$

$\mathrm{PadRight}\left(''foo''\,6\right)$

$''foo''$

$\mathrm{Center}\left(''foo''\,5\right)$

$''foo''$

$\mathrm{Center}\left(''foo''\,6\right)$

$''foo''$

$\mathrm{PadLeft}\left(''foo''\,8\,''x''\right)$

$''xxxxxfoo''$

$\mathrm{PadRight}\left(''foo''\,8\,''x''\right)$

$''fooxxxxx''$

$\mathrm{Center}\left(''foo''\,8\,''x''\right)$

$''xxxfooxx''$

$\mathrm{TrimLeft}\left(\mathrm{PadLeft}\left(''foo''\,17\right)\right)$

$''foo''$

$\mathrm{TrimRight}\left(\mathrm{PadRight}\left(''foo''\,17\right)\right)$

$''foo''$

$\mathrm{Trim}\left(\mathrm{Center}\left(''foo''\,17\right)\right)$

$''foo''$

$\mathrm{TrimLeft}\left(\mathrm{PadLeft}\left(''foo''\,17\right)\right)$

$''foo''$