Port grep utility to meniOS

[pbalduino]

Description

Port the grep utility to meniOS to enable pattern matching and text searching in files from the shell.

Requirements

Implement a basic grep utility with essential functionality:

• grep PATTERN FILE - Search for pattern in file
• grep PATTERN - Search for pattern in stdin (for use in pipelines)
• Support for basic regular expressions or simple string matching
• Exit status: 0 if match found, 1 if no match, 2 on error
• Basic flags (optional):
  • -i - Case-insensitive matching
  • -v - Invert match (show non-matching lines)
  • -n - Show line numbers
  • -c - Count matching lines

Implementation Details

The utility should:

• Work with the existing file I/O syscalls (open, read, close)
• Handle stdin for pipeline support (e.g., cat file.txt | grep foo)
• Use the userland libc for string operations
• Follow POSIX-like conventions for grep behavior
• Handle edge cases (empty files, binary files, no matches)

Usage Examples

$ grep "error" /var/log/system.log
error: Failed to mount device

$ cat file.txt | grep "TODO"
// TODO: Fix this function

$ grep -n "main" program.c
42:int main(int argc, char **argv) {

Dependencies

• #193 - Minimal userland libc ✅ (COMPLETE)
• #60 - Filesystem syscalls ✅ (COMPLETE)
• #102 - Pipes implementation ✅ (COMPLETE - for pipeline support)

Acceptance Criteria

• [ ] grep PATTERN FILE searches file for pattern
• [ ] grep PATTERN reads from stdin for pipeline usage
• [ ] Proper exit status codes (0/1/2)
• [ ] Basic pattern matching works (literal strings at minimum)
• [ ] Works in pipelines with other utilities
• [ ] Test coverage for grep functionality
• [ ] Documentation/man page entry

Estimated Effort

2-3 days

Priority

Medium - Useful utility for text processing and debugging

Milestone

Consider for future utility expansion after Mosh milestone completion