Write a shell script to locate executable files

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
Outline for Programming Assignment 1
Attached Files:

    File Assignment1-Example.pdf (12.262 KB) 

The PDF file has a flow chart example of how to program Assignment 1.

Here is some psuedo code:

BEGIN
    set FINDALL to false
    IF $1 equals -a THEN
        set FINDALL to TRUE
        dispose of $1
    END-IF
    FOR each Positional Parameter ($file) DO
        IF $file is a pathname THEN
            IF if $file is executable and not a directory THEN
                echo $file
            ELSE
                echo $file  is NOT Found
            END-IF
        ELSE
            set FOUND to false
            # Don't forget to handle the special cases of PATH
            FOR  P in PATH (: separated list) DO
                IF $P/$file is executable and not a directory THEN
                    set FOUND to true
                    echo $P/$file
                    IF FINDALL is FALSE THEN
                        BREAK FROMTHE for  LOOP
                    END-IF
                ELSE
                END-IF
                IF FOUND is FALSE THEN
                    echo $file is NOT FOUND
                END-IF
            END-FOR
        END-IF
    END-FOR
END