In /usr/bin/eqn2graph line 68:
if ! tmp=`(umask 077 && mktemp -d -q "$d/eqn2graph-XXXXXX") 2> /dev/null`
         ^-- SC2006: Use $(...) notation instead of legacy backticked `...`.

Did you mean: 
if ! tmp=$((umask 077 && mktemp -d -q "$d/eqn2graph-XXXXXX") 2> /dev/null)


In /usr/bin/eqn2graph line 87:
is_convert_recent=`convert -help | grep -e -trim`
                  ^-----------------------------^ SC2006: Use $(...) notation instead of legacy backticked `...`.

Did you mean: 
is_convert_recent=$(convert -help | grep -e -trim)


In /usr/bin/eqn2graph line 94:
trap 'exit_status=$?; rm -rf "$tmp" && exit $exit_status' EXIT INT TERM
     ^-- SC2154: exit_status is referenced but not assigned.


In /usr/bin/eqn2graph line 101:
read equation
^--^ SC2162: read without -r will mangle backslashes.


In /usr/bin/eqn2graph line 104:
	&& convert $convert_trim_arg $convert_opts "$tmp"/eqn2graph.ps \
                   ^---------------^ SC2086: Double quote to prevent globbing and word splitting.
                                     ^-----------^ SC2086: Double quote to prevent globbing and word splitting.

Did you mean: 
	&& convert "$convert_trim_arg" "$convert_opts" "$tmp"/eqn2graph.ps \


In /usr/bin/eqn2graph line 105:
	   "$tmp"/eqn2graph.$format \
                            ^-----^ SC2086: Double quote to prevent globbing and word splitting.

Did you mean: 
	   "$tmp"/eqn2graph."$format" \


In /usr/bin/eqn2graph line 106:
	&& cat "$tmp"/eqn2graph.$format
                                ^-----^ SC2086: Double quote to prevent globbing and word splitting.

Did you mean: 
	&& cat "$tmp"/eqn2graph."$format"

For more information:
  https://www.shellcheck.net/wiki/SC2154 -- exit_status is referenced but not...
  https://www.shellcheck.net/wiki/SC2086 -- Double quote to prevent globbing ...
  https://www.shellcheck.net/wiki/SC2162 -- read without -r will mangle backs...