In /usr/bin/gettext.sh line 20:
if test "X`(echo '\t') 2>/dev/null`" = 'X\t'; then
          ^-----------------------^ SC2006: Use $(...) notation instead of legacy backticked `...`.
                 ^--^ SC2028: echo may not expand escape sequences. Use printf.

Did you mean: 
if test "X$((echo '\t') 2>/dev/null)" = 'X\t'; then


In /usr/bin/gettext.sh line 23:
  if test "X`(printf '%s\n' '\t') 2>/dev/null`" = 'X\t'; then
            ^-- SC2006: Use $(...) notation instead of legacy backticked `...`.

Did you mean: 
  if test "X$((printf '%s\n' '\t') 2>/dev/null)" = 'X\t'; then


In /usr/bin/gettext.sh line 31:
    echo='echo_func'
    ^--^ SC2034: echo appears unused. Verify use (or export if used externally).


In /usr/bin/gettext.sh line 88:
  gettext "$1" | (export PATH `envsubst --variables "$1"`; envsubst "$1")
                         ^--^ SC2030: Modification of PATH is local (to subshell caused by (..) group).
                              ^-------------------------^ SC2046: Quote this to prevent word splitting.
                              ^-------------------------^ SC2006: Use $(...) notation instead of legacy backticked `...`.

Did you mean: 
  gettext "$1" | (export PATH $(envsubst --variables "$1"); envsubst "$1")


In /usr/bin/gettext.sh line 95:
  ngettext "$1" "$2" "$3" | (export PATH `envsubst --variables "$1 $2"`; envsubst "$1 $2")
                                    ^--^ SC2031: PATH was modified in a subshell. That change might be lost.
                                         ^----------------------------^ SC2046: Quote this to prevent word splitting.
                                         ^----------------------------^ SC2006: Use $(...) notation instead of legacy backticked `...`.

Did you mean: 
  ngettext "$1" "$2" "$3" | (export PATH $(envsubst --variables "$1 $2"); envsubst "$1 $2")

For more information:
  https://www.shellcheck.net/wiki/SC2034 -- echo appears unused. Verify use (...
  https://www.shellcheck.net/wiki/SC2046 -- Quote this to prevent word splitt...
  https://www.shellcheck.net/wiki/SC2028 -- echo may not expand escape sequen...