In /usr/bin/gsl-config line 4:
exec_prefix=/usr
^---------^ SC2034: exec_prefix appears unused. Verify use (or export if used externally).


In /usr/bin/gsl-config line 5:
includedir=/usr/include
^--------^ SC2034: includedir appears unused. Verify use (or export if used externally).


In /usr/bin/gsl-config line 26:
    exit $1
         ^-- SC2086: Double quote to prevent globbing and word splitting.

Did you mean: 
    exit "$1"


In /usr/bin/gsl-config line 33:
cflags=false
^----^ SC2034: cflags appears unused. Verify use (or export if used externally).


In /usr/bin/gsl-config line 34:
libs=false
^--^ SC2034: libs appears unused. Verify use (or export if used externally).


In /usr/bin/gsl-config line 38:
    -*=*) optarg=`echo "$1" | sed 's/[-_a-zA-Z0-9]*=//'` ;;
                 ^-- SC2006: Use $(...) notation instead of legacy backticked `...`.

Did you mean: 
    -*=*) optarg=$(echo "$1" | sed 's/[-_a-zA-Z0-9]*=//') ;;


In /usr/bin/gsl-config line 48:
	echo $prefix
             ^-----^ SC2086: Double quote to prevent globbing and word splitting.

Did you mean: 
	echo "$prefix"


In /usr/bin/gsl-config line 65:
        : ${GSL_CBLAS_LIB=-lgslcblas}
          ^-------------------------^ SC2223: This default assignment may cause DoS due to globbing. Quote it.

For more information:
  https://www.shellcheck.net/wiki/SC2034 -- cflags appears unused. Verify use...
  https://www.shellcheck.net/wiki/SC2086 -- Double quote to prevent globbing ...
  https://www.shellcheck.net/wiki/SC2223 -- This default assignment may cause...