Make sh scrips POSIX compliant

Using shellcheck, I went through all of them to make them standards
compliant. I also tested as many as I could.

1 files changed, 5 insertions, 6 deletions

diff --git a/shasum b/shasum
index 18efefd..ce40ba2 100755
--- a/shasum
+++ b/shasum
@@ -1,22 +1,21 @@
 #!/bin/sh
 
-for i in "$@"; do
+for i; do
   case $i in
     "-a") BITS="y"
       continue
       ;;
     *)
-      ARGS="$i "
+      ARGS="$i"
       ;;
   esac
   if [ -n "$BITS" ]; then
-    case $i in
+    case "$i" in
       256|512)
-        PROGRAM="sha"$i"sum"
+        PROGRAM="sha${i}sum"
         ;;
     esac
     unset BITS
   fi
 done
-cat - | "$PROGRAM" $ARGS
-echo "$PROGRAM $ARGS"
+"$PROGRAM" ${ARGS:+"$ARGS"}