CSE 333 25au Exercise 7

out: Friday, October 10, 2025
due: Monday, October 13, 2025 by 10:00 am, No late exercises accepted.

Goals: Learn to use POSIX I/O routines to scan a file directory and read the contents of selected files. These routines will be needed in later parts of the large project sequence. This exercise provides a chance to learn how to use them in a much simpler setting without additional complications of the larger project.

Description: Write a C program that:

• accepts a directory name as a command-line argument. The directory name can be a simple name or a longer file path; it might, or might not, have a leading '/' at the beginning; and might, or might not, have a trailing '/' at the end.
• scans through the directory looking for filenames that end in the four characters .txt. You should not scan subdirectories, and you do not need to sort the directory entries; you may also assume that no subdirectory itself has a directory name ending in .txt.
• reads the contents of those files using the POSIX open / read / close functions, copying the contents to stdout. You may use C standard library functions (hint: fwrite) to write to stdout, but you must use open / read / close to read the files.

Note: do not format, label, or otherwise add to, delete from, or modify the contents of files copied to stdout. Copy the bytes from the input file(s) exactly as they are with no changes.

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Your code must:

• compile without errors or warnings on CSE Linux machines (lab workstations, attu, or CSE home VM).
• have no crashes, memory leaks, or memory errors on CSE linux machines. (Suggestion: valgrind)
• be contained in a single file called ex7.c that compiles with the command gcc -Wall -g -std=c17 -o ex7 ex7.c -- do not submit a Makefile.
• be pretty: the formatting, modularization, variable and function names, and so on must make us smile rather than cry. (Suggestion: cpplint --clint.
• be robust: you should think about handling bogus input from the user (if any), and you should handle hard-to-handle cases (if there are any) gracefully. Hint: be sure to test your code with text files that have lines that are both shorter and longer than the input buffer you use with read.
• have a comment at the top of the source file with your name, and CSE or UW email address.

You should submit your exercise using the Gradescope dropbox linked on the course resources web page.