Write a shell script to locate executable files. This script takes a list of fil

Question

Write a shell script to locate executable files. This script takes a list of file names from the command line and determines which would be executed had these names been given as commands.

The search path should be based only on the user's PATH environment variable. You shall not use the Unix which command, the ksh whence (type) command, the locate command, or the bash type command.

The code for the script shall not use the UNIX ls command to determine if the file is executable or if it exists.

The script should find only the first occurrence of the "file". If the file is not found, the script the following

<command>NOT FOUND

<command> would be replaced by the name of the "file" you didn't find.

If the first parameter is '-a', then the script should print all occurrences of the executable file in the user's path. Again if the file was not on the path, an error message should be displayed.

The find command shall not be used.

A project using temporary files will not be graded.

Note: The shell variable PATH defines the search path for the directory containing the command. Alternative directory names are separated by a colon (:). The current directory can be specified by two or more adjacent colons, or by a colon at the beginning or end of the path list.

If the command name contains a / then the search path is not used, you just check if the command/file specified is executable and not a directory. Otherwise, each directory in the path is searched for an executable file.

usage: mywhich [-a] command ....

Examples: The locations of these programs may vary on different systems and the users PATH environment variable.

prompt> mywhich

ls /bin/ls

prompt> mywhich -a cc

/bin/cc

/usr/ucb/cc

prompt> mywhich ./mywhich

./mywhich

prompt> mywhich /bin/ls

/bin/ls

prompt> mywhich fooblar

fooblar not found

prompt> mywhich ksh sh csh bash

/usr/bin/ksh

/bin/sh

/bin/csh

/usr/local/bin/bash

Explanation / Answer

#!/bin/bash

echo "$1 $2"

FINDALL=FALSE

case $PATH in

:*)
    PATH=".:$PATH"
    ;;
*::*)
    PATH=`echo $PATH | sed -e 's/::/:.:/g'`
    ;;
*:)
    PATH="$PATH:."
    ;;

IFS=$OLDIFS
IFS=:
set -- $PATH
IFS=$OLDIFS

esac
command="$1"

case $command in
*/*)
    echo $command
    ;;

-a)
echo "-a stuff first $1 $2"
shift
command="$1"
echo "after shift $1"
echo "$command"
FOUND=false
IFS=:
    for P in $PATH
                do
                  if [ ! -d "$P/$command" -a -x "$P/$command" ]
                        then
                        FOUND=true
                        echo $P/$command
                      continue
                  fi done

                  if [ "$FOUND" = false ]
                        then
                        echo "Command $command not found in your
search path"
                  fi
   ;;

*)
   FOUND=false
      for P
          do

            if [ ! -d "$P/$command" -a -x "$P/$command" ]
                  then
                  FOUND=true
                  echo $P/$command
                  break
            fi done

            if [ "$FOUND" = false ]
                  then
                  echo "Command $command not found in your search
path"
            fi
;;

esac

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