more conventional exceptions for abstract syntax operations -- eliminated ancient SYS_ERROR;
proper signature constraint;
#!/usr/bin/env bash
#
# fileident --- produce file identification based
FILE="$1"
if [ -n "$ISABELLE_FILE_IDENT" -a -f "$FILE" -a -r "$FILE" ]
then
ID=$(cat "$FILE" | $ISABELLE_FILE_IDENT | cut -d " " -f 1) && echo -n "$ID"
fi