CSC 271
Homework 3

Assigned 30 Oct
Due 11 Nov

Write two shell scripts (either csh or sh).

The first, backup, takes a filename as an argument and makes an appropriately-named backup copy of it. If, for example, the filename argument is foo.c, the backup copy should be named foo.c.backup.1. But if there's already a file by that name in the current directory, your script will try foo.c.backup.2, foo.c.backup.3, and so on until it finds a name that isn't already taken.
For extra credit, add any or all of the following features:
- allow multiple filenames as arguments: each one is backed up individually, so "backup foo.c foo.h Makefile" is equivalent to "backup foo.c; backup foo.h; backup Makefile".
- take an optional final argument which is a directory in which to search for old backups, and put the new one. If the optional argument is not provided, use the current directory.
- check the value of a particular environment variable (say, "BACKUP_DIRECTORY") for a directory in which to search for old backups and put the new one; if this variable is undefined, use the current directory.
The second, lastbackup, is intended for retrieving the last-saved version of a specified file. If the user types, for example, "lastbackup foo.c", your program will search through all the backups of foo.c for the one with the highest version number, and retrieve it. "Retrieve" may mean any of several things (choose one and state clearly which one you've chosen): copy the backed-up version to foo.c, overwriting the current version; output the backed-up version to stdout, so the user can redirect or pipe it as desired; or simply output the name of the backed-up version.
For extra credit, implement one of these three definitions of "retrieve" by default and provide options (e.g. "-n" to output the name, "-p" to act as a pipe and output the file itself to stdout) to allow the user to choose one of the other behaviors.

Last modified: Thu Oct 30 14:34:35 EST 1997

Stephen Bloch / sbloch@boethius.adelphi.edu

CSC 271 Homework 3

Assigned 30 Oct Due 11 Nov

CSC 271
Homework 3

Assigned 30 Oct
Due 11 Nov