Laboratory 1

These two programming problems will introduce you to systems programming. Although you may use any system to develop the programs on, you must ensure they run on the Linux systems in the CSIF.

Timeout Program (60 points)

Write a program that terminates a second program after a given period of time. Your program is to have the following interface:

timeout s command ... 

When this command is issued, the timeout program is to execute command .... After s seconds have passed, timeout is to send a SIGTERM signal to command ..... You must use fork(2) and execve(2) to run the subcommand. Don’t forget to check for possible errors, such as a negative number of seconds or no command!

Extending tee (40 points)

Write a program called etee that takes its standard input and copies it to its standard output, saving a copy in a file. The interface is

etee [ -a ] file

where file is the file to which the output is to be saved. If the “a” flag is given, the output is to be appended to file. If file has the name “–n”, where n is an integer, the copy of the output is to be written to file descriptor n. So, for example, the command

etee -2

will copy its input to both its standard output and the standard error (which corresponds to file descriptor 2).

Extra Credit Problems

1. (10 points) In the first problem, use the search path as defined by the PATH environment variable to locate the command.