Arg handling in a script for a modified “find” function?

Question

I'm using FreeBSD and I understand and use the -prune option on find to prevent the command descending into a subdirectory. But I find the necessary syntax very clumsy and awkward. It also doesn't prevent the pruned dir itself showing up which is fixable but annoying.

I'd like to create a short script/alias which has the effect of adding a new -noenter arg to the find command if it's given before any other primaries (for simplicity).

The aim is that I can type either of:

• find -xs /dir -noenter '$*' -name '*.conf' -ls
• find -x -s /dir -noenter '$*' -name '*.conf' -ls

and it'll convert the args and execute:

• /usr/bin/find -xs /dir \( -name '$*' -prune -or \( -name '*.conf' -and ! \( -type d -and -name '$*' \) \) \) -ls
• /usr/bin/find -x -s /dir \( SNIPPED \) -ls

but I can also type as normal any routine "find" command and it'll pass it transparently to /usr//bin/find to execute.

Logically the script needs to identify the first arg after the dir name, and then test if it's:

• ... equal to -noenter and followed by at least 2 more args (in which case I know how to build the arg I need to pass to /usr/bin/find by knowing which args were before/after it); or
• ... equal to -noenter but not followed by at least 2 more args (= error); or
• ...anything else or dir was the last arg or wasn't found (= pass entire original args to /usr/bin/find unaltered).

I can do all of this except one thing - how do I code the part of the script that examines argv to tell which arg number (if any) is the dir argument?

My choice of shell is sh for scripting.

Answer 1

If what you want is to test for the existence and location of a specific argument, all you need to do is parse the command line and test each argument for a match with your "expected" value. So, you need to test each argument for the value -noenter and then print a line stating the position and name of the variable -noenter:

for i in `seq 1 $#`; do
    ref=`eval "echo \\$$i"`
    if [ $ref == '-noenter' ]; then echo "arg $i is $ref"; break; fi
done

Now the same thing, only the position of the argument -noenter is stored in $mitsos and the position of the argument before that in $mary:

for i in `seq 1 $#`; do
  ref=`eval "echo \\${$i}"`
  if [ $ref == '-noenter' ]; then
    mitsos=$i
    eva=$(($i-1))
    mary=`eval "echo \\${$eva}"`
    break
  fi
done

and now $mitsos has the position of -noenter or no value and $mary the value of the argument preceding -noenter. At this point, if $mary has the value /dir you know the next argument is -noenter and you may continue with your implementation of find, otherwise you use the system's version or print an error message. Finally, if you don't care for the position of -noenter you may omit the line mitsos=$i.