How do I find the last argument in a Bourne shell script?

If you are sure the number of arguments is at most 9, you can use: eval last=\${$#}

In POSIX-compatible shells it works for ANY number of arguments. The following works always too: for last

do 
     : done

This can be generalized as follows: for i

do
      third_last=$second_last second_last=$last last=$i done

Now suppose you want to REMOVE the last argument from the list, or REVERSE the argument list, or ACCESS the N-th argument directly, whatever N may be. Here is a basis of how to do it, using only builtin shell constructs, without creating subprocesses: 

t0= u0= rest=‘1 2 3 4 5 6 7 8 9’ argv= 
     for h in ‘‘ $rest do for t in “$t0” $rest do 
     for u in $u0 $rest do case $# in 0) break 3
           esac eval
           argv$h$t$u=\$1
           argv=“$argv \”\$argv$h$t$u\”“ # (1)
      shift done u0=0
done t0=0
done # now restore the arguments eval set x “$argv”
# (2) shift 

This example works for the first 999 arguments. Enough? Take a good look at the lines marked (1) and (2) and convince yourself that the original arguments are restored indeed, no matter what funny characters they contain!

To find the N-th argument now you can use this: eval argN=\$argv$N

To reverse the arguments the line marked (1) must be changed to:
argv=“\”\$argv$h$t$u\” $argv”

How to remove the last argument is left as an exercise.

If you allow subprocesses as well, possibly executing nonbuilt-in commands, the
`argvN’ variables can be set up more easily: N=1

for i
do
eval argv$N=\$i N=`expr $N + 1`
done

To reverse the arguments there is still a simpler method, that even does not create subprocesses. This approach can also be taken if you want to delete e.g. the last argument, but in that case you cannot refer directly to the N-th argument anymore, because the `argvN’ variables are set up in reverse order: argv=

for i

do
     eval argv$#=\$i argv=“\”\$argv$#\” $argv”
     shift done

eval set x “$argv”
shift

Relevance Read:

• How does a kill Process Work

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