minicoreutils

Tiny from-scratch rewrites of cat, echo, and grep in C, built to get comfortable with the standard I/O and string libraries before moving on to bigger systems work.

Overview

Three single-file utilities that mirror the basic behavior of their GNU coreutils namesake. No external dependencies beyond the C standard library. The goal is to learn development in an embedded environment as well as learning how memory management works and to get the core file I/O and string-handling patterns down by simply reading a file byte-by-byte, walking argv, and scanning line buffers.

Utilities

Program	Mirrors	What it does
cat.c	cat	Opens each file argument and streams its contents to stdout one character at a time via fgetc.
echo.c	echo	Prints its arguments space-separated. Supports -n to suppress the trailing newline.
grep.c	grep	Reads each file line-by-line into a fixed 2048-byte buffer and prints any line containing the search term via strstr.

Notes

• cat and grep both fail gracefully per-file. The program prints an error if one file in the argument list can't be opened and continues with the rest rather than just exiting.
• grep uses a fixed-size line buffer rather than dynamic allocation, so it's a simplified single-substring matcher, not a real regex engine.
• Flags for line numbers, recursion, and case-insensitivity were left out on purpose to keep the first pass focused on plain file I/O.

Building and Running

Just a standard C compiler (GCC / Clang). Each utility compiles independently.

Linux / macOS

gcc cat.c -o cat
gcc echo.c -o echo
gcc grep.c -o grep

Windows (MinGW / GCC)

gcc cat.c -o cat.exe
gcc echo.c -o echo.exe
gcc grep.c -o grep.exe

Usage

./cat file.txt
./echo -n hello world
./grep search_term file.txt

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