Apply runtime shebanging to POSIX shell

1 files changed, 62 insertions, 0 deletions

diff --git a/bin/apf.sh b/bin/apf.sh
new file mode 100644
index 00000000..5e40e9b8
--- /dev/null
+++ b/bin/apf.sh
@@ -0,0 +1,62 @@
+# Prepend arguments from a file to the given arguments for a command
+self=apf
+
+# Require at least two arguments
+if [ "$#" -lt 2 ] ; then
+    printf >&2 '%s: Need an arguments file and a command\n' "$self"
+    exit 2
+fi
+
+# First argument is the file containing the null-delimited arguments
+argf=$1 cmd=$2
+shift 2
+
+# If there were arguments given on the command line, we need to be careful and
+# prepend our ones first
+if [ "$#" -gt 0 ] ; then
+
+    # Iterate through any remaining arguments
+    for carg ; do
+
+        # If this is the first command argument, then before we add it, we'll
+        # add all the ones from the file first if it exists
+        if [ -n "$argf" ] ; then
+
+            # Reset the positional parameters
+            set --
+
+            # Put our file arguments in first before we continue with the loop
+            if [ -e "$argf" ] ; then
+                while IFS= read -r farg ; do
+                    case $farg in
+                        '#'*) continue ;;
+                        *[![:space:]]*) ;;
+                        *) continue ;;
+                    esac
+                    set -- "$@" "$farg"
+                done < "$argf"
+            fi
+
+            # Unset the argfile so we don't repeat this bit
+            unset -v argf
+        fi
+
+        # Stack the original invocation argument back onto the positional
+        # parameters
+        set -- "$@" "$carg"
+    done
+
+# If there weren't, we can just read the file and slap them in
+elif [ -e "$argf" ] ; then
+    while IFS= read -r farg ; do
+        case $farg in
+            '#'*) continue ;;
+            *[![:space:]]*) ;;
+            *) continue ;;
+        esac
+        set -- "$@" "$farg"
+    done < "$argf"
+fi
+
+# Run the command with the changed arguments
+exec "$cmd" "$@"