gorep

A small, fast grep-like tool written in Go. gorep searches text for a regular expression and prints matching lines with colored highlights. It supports reading from stdin, searching an inline string, a file, or recursively searching files in a directory.

Key Features

• Pattern search using Go regular expressions (regexp).
• Colored output: matches highlighted in green, file/line labels in red/white (via fortio.org/terminal/ansipixels/tcolor).
• Supports reading from stdin, a single file, or a directory (recurses into subdirectories).
• -no-trim option to preserve leading whitespace in printed lines.

Requirements

• Go (1.18+ recommended). Verify with go version.

Build

go mod tidy
go build -o gorep .

Run (examples)

• Search piped input:

echo "hello world" | gorep "world"

• Search an inline string (pattern then text):

gorep "foo" "this is foo and that is bar"

• Search a file:

gorep "TODO" -f README.md

• Search a directory (recursively):

gorep "TODO" -f ./src

Flags

• -f <path> : read input from a file or directory. If a directory is provided, gorep will walk the directory and search files it can read.
• -no-trim : disable trimming leading indentation in each printed line. By default gorep trims leading tabs/spaces around matches.
• -o <path> : path to output file, where gorep will write each match

Behavior details

• The first non-flag argument is treated as the regular expression pattern. If it includes a space, it should be inside quotation marks ""
• If additional non-flag arguments are provided after the pattern they are joined into a single input string to search (convenient for one-off searches from the CLI).
• If no -f is provided and no inline text is given, gorep reads from stdin until EOF.
• Matches in a line are highlighted in green; printed lines are numbered and prefixed with color-coded labels. When searching directories, each file's results are prefixed by the filename.

Limitations & Notes

• The directory traversal implementation changes the working directory while recursing; if you rely on a stable working directory in other parts of a larger script, be cautious.
• Files that cannot be read are skipped silently when walking directories.
• Errors (invalid regexp, unreadable file, etc.) will log a message and exit with a non-zero status.

Testing

go test ./...

Contributing

• Open issues or pull requests. Small, focused changes are easiest to review.

Source

• Main implementation: main.go