Assignment 1 Announcements

Sept 24: Tid bits

Since some of the same questions keep popping up, here are a few answers:

You can assume that the program is run as "mywhich [options] progname [...]" In other words you can assume that all of the options will come before all of the strings that you want to match with executable files.
Each element of the PATH variable is represents a single directory. The full path to the directory is given because you need to know where each directory is. Your program will not search any subdirectories of that directory.
Remember that "~" and "~user" mean different things. the skip-tilde option only applies to directories that begin with "~/". However, if you try the skip-tilde option with "which" you will discover that any directory beginning with your home directory will be skipped. Your program should follow the behaviour of "which".
Which executable permissions should I care about: user, group, other? Check that at least one of them is set.

Sept 23: getopt_long

Here's the code for the example used in tutorial: try_getopt_verbose.c".

Sept 17: getenv: The getenv function uses a statically declared character buffer in which to put the value of the environment variable that you passed in as an argument. This means that you may sometimes get odd behaviour if you try to manipulate the pointer that getenv returns or modify the contents of the buffer. The solution is to copy the string to a buffer you have declared.
Also, you should probably follow the instructions in the man page for strtok and not use it. You will then need to write your own code for traversing the character buffer.

Sept 16: Do your experimentation on Linux: Solaris has a version of which that has many fewer options, so you won't get the same behaviour if you try it out on the Sun machines. Log into one of the Linux machines and try it there.

Sept 16: which which: The version of which that is built into tcsh (the default shell on cdf) differs from the man page description. To run the version of which that the man page describes, try running "/usr/bin/which". Alternatively, you could switch to the bash shell temporarily, by typing "bash" (type "exit" to return to your regular shell).

Last modified: Tue Sep 24 17:52:38 EDT 2002